JAC Class 12 Maths Solutions in Hindi & English Jharkhand Board

JAC Jharkhand Board Class 12th Maths Solutions in Hindi & English Medium

JAC Board Class 12th Maths Solutions in English Medium

JAC Class 12 Maths Chapter 1 Relations and Functions

  • Chapter 1 Relations and Functions Ex 1.1
  • Chapter 1 Relations and Functions Ex 1.2
  • Chapter 1 Relations and Functions Ex 1.3
  • Chapter 1 Relations and Functions Ex 1.4
  • Chapter 1 Relations and Functions Miscellaneous Exercise

JAC Class 12 Maths Chapter 2 Inverse Trigonometric Functions

  • Chapter 2 Inverse Trigonometric Functions Ex 2.1
  • Chapter 2 Inverse Trigonometric Functions Ex 2.2
  • Chapter 2 Inverse Trigonometric Functions Miscellaneous Exercise

JAC Class 12 Maths Chapter 3 Matrices

  • Chapter 3 Matrices Ex 3.1
  • Chapter 3 Matrices Ex 3.2
  • Chapter 3 Matrices Ex 3.3
  • Chapter 3 Matrices Ex 3.4
  • Chapter 3 Matrices Miscellaneous Exercise

JAC Class 12 Maths Chapter 4 Determinants

  • Chapter 4 Determinants Ex 4.1
  • Chapter 4 Determinants Ex 4.2
  • Chapter 4 Determinants Ex 4.3
  • Chapter 4 Determinants Ex 4.4
  • Chapter 4 Determinants Ex 4.5
  • Chapter 4 Determinants Ex 4.6
  • Chapter 4 Determinants Miscellaneous Exercise

JAC Class 12 Maths Chapter 5 Continuity and Differentiability

  • Chapter 5 Continuity and Differentiability Ex 5.1
  • Chapter 5 Continuity and Differentiability Ex 5.2
  • Chapter 5 Continuity and Differentiability Ex 5.3
  • Chapter 5 Continuity and Differentiability Ex 5.4
  • Chapter 5 Continuity and Differentiability Ex 5.5
  • Chapter 5 Continuity and Differentiability Ex 5.6
  • Chapter 5 Continuity and Differentiability Ex 5.7
  • Chapter 5 Continuity and Differentiability Ex 5.8
  • Chapter 5 Continuity and Differentiability Miscellaneous Exercise

JAC Class 12 Maths Chapter 6 Application of Derivatives

  • Chapter 6 Application of Derivatives Ex 6.1
  • Chapter 6 Application of Derivatives Ex 6.2
  • Chapter 6 Application of Derivatives Ex 6.3
  • Chapter 6 Application of Derivatives Ex 6.4
  • Chapter 6 Application of Derivatives Ex 6.5
  • Chapter 6 Application of Derivatives Miscellaneous Exercise

JAC Class 12 Maths Chapter 7 Integrals

  • Chapter 7 Integrals Ex 7.1
  • Chapter 7 Integrals Ex 7.2
  • Chapter 7 Integrals Ex 7.3
  • Chapter 7 Integrals Ex 7.4
  • Chapter 7 Integrals Ex 7.5
  • Chapter 7 Integrals Ex 7.6
  • Chapter 7 Integrals Ex 7.7
  • Chapter 7 Integrals Ex 7.8
  • Chapter 7 Integrals Ex 7.9
  • Chapter 7 Integrals Ex 7.10
  • Chapter 7 Integrals Ex 7.11
  • Chapter 7 Integrals Miscellaneous Exercise

JAC Class 12 Maths Chapter 8 Application of Integrals

  • Chapter 8 Application of Integrals Ex 8.1
  • Chapter 8 Application of Integrals Ex 8.2
  • Chapter 8 Application of Integrals Miscellaneous Exercise

JAC Class 12 Maths Chapter 9 Differential Equations

  • Chapter 9 Differential Equations Ex 9.1
  • Chapter 9 Differential Equations Ex 9.2
  • Chapter 9 Differential Equations Ex 9.3
  • Chapter 9 Differential Equations Ex 9.4
  • Chapter 9 Differential Equations Ex 9.5
  • Chapter 9 Differential Equations Ex 9.6
  • Chapter 9 Differential Equations Miscellaneous Exercise

JAC Class 12 Maths Chapter 10 Vector Algebra

  • Chapter 10 Vector Algebra Ex 10.1
  • Chapter 10 Vector Algebra Ex 10.2
  • Chapter 10 Vector Algebra Ex 10.3
  • Chapter 10 Vector Algebra Ex 10.4
  • Chapter 10 Vector Algebra Miscellaneous Exercise

JAC Class 12 Maths Chapter 11 Three Dimensional Geometry

  • Chapter 11 Three Dimensional Geometry Ex 11.1
  • Chapter 11 Three Dimensional Geometry Ex 11.2
  • Chapter 11 Three Dimensional Geometry Ex 11.3
  • Chapter 11 Three Dimensional Geometry Miscellaneous Exercise

JAC Class 12 Maths Chapter 12 Linear Programming

  • Chapter 12 Linear Programming Ex 12.1
  • Chapter 12 Linear Programming Ex 12.2
  • Chapter 12 Linear Programming Miscellaneous Exercise

JAC Class 12 Maths Chapter 13 Probability

  • Chapter 13 Probability Ex 13.1
  • Chapter 13 Probability Ex 13.2
  • Chapter 13 Probability Ex 13.3
  • Chapter 13 Probability Ex 13.4
  • Chapter 13 Probability Ex 13.5
  • Chapter 13 Probability Miscellaneous Exercise

JAC Board Class 12th Maths Solutions in Hindi Medium

JAC Class 12 Maths Chapter 1 संबंध एवं फलन

  • Chapter 1 संबंध एवं फलन Ex 1.1
  • Chapter 1 संबंध एवं फलन Ex 1.2
  • Chapter 1 संबंध एवं फलन Ex 1.3
  • Chapter 1 संबंध एवं फलन Ex 1.4
  • Chapter 1 संबंध एवं फलन विविध प्रश्नावली

JAC Class 12 Maths Chapter 2 प्रतिलोम त्रिकोणमितीय फलन

  • Chapter 2 प्रतिलोम त्रिकोणमितीय फलन Ex 2.1
  • Chapter 2 प्रतिलोम त्रिकोणमितीय फलन Ex 2.2
  • Chapter 2 प्रतिलोम त्रिकोणमितीय फलन विविध प्रश्नावली

JAC Class 12 Maths Chapter 3 आव्यूह

  • Chapter 3 आव्यूह Ex 3.1
  • Chapter 3 आव्यूह Ex 3.2
  • Chapter 3 आव्यूह Ex 3.3
  • Chapter 3 आव्यूह Ex 3.4
  • Chapter 3 आव्यूह विविध प्रश्नावली

JAC Class 12 Maths Chapter 4 सारणिक

  • Chapter 4 सारणिक Ex 4.1
  • Chapter 4 सारणिक Ex 4.2
  • Chapter 4 सारणिक Ex 4.3
  • Chapter 4 सारणिक Ex 4.4
  • Chapter 4 सारणिक Ex 4.5
  • Chapter 4 सारणिक Ex 4.6
  • Chapter 4 सारणिक विविध प्रश्नावली

JAC Class 12 Maths Chapter 5 सांतत्य तथा अवकलनीयता

  • Chapter 5 सांतत्य तथा अवकलनीयता Ex 5.1
  • Chapter 5 सांतत्य तथा अवकलनीयता Ex 5.2
  • Chapter 5 सांतत्य तथा अवकलनीयता Ex 5.3
  • Chapter 5 सांतत्य तथा अवकलनीयता Ex 5.4
  • Chapter 5 सांतत्य तथा अवकलनीयता Ex 5.5
  • Chapter 5 सांतत्य तथा अवकलनीयता Ex 5.6
  • Chapter 5 सांतत्य तथा अवकलनीयता Ex 5.7
  • Chapter 5 सांतत्य तथा अवकलनीयता Ex 5.8
  • Chapter 5 सांतत्य तथा अवकलनीयता विविध प्रश्नावली

JAC Class 12 Maths Chapter 6 अवकलज के अनुप्रयोग

  • Chapter 6 अवकलज के अनुप्रयोग Ex 6.1
  • Chapter 6 अवकलज के अनुप्रयोग Ex 6.2
  • Chapter 6 अवकलज के अनुप्रयोग Ex 6.3
  • Chapter 6 अवकलज के अनुप्रयोग Ex 6.4
  • Chapter 6 अवकलज के अनुप्रयोग Ex 6.5
  • Chapter 6 अवकलज के अनुप्रयोग विविध प्रश्नावली

JAC Class 12 Maths Chapter 7 समाकलन

  • Chapter 7 समाकलन Ex 7.1
  • Chapter 7 समाकलन Ex 7.2
  • Chapter 7 समाकलन Ex 7.3
  • Chapter 7 समाकलन Ex 7.4
  • Chapter 7 समाकलन Ex 7.5
  • Chapter 7 समाकलन Ex 7.6
  • Chapter 7 समाकलन Ex 7.7
  • Chapter 7 समाकलन Ex 7.8
  • Chapter 7 समाकलन Ex 7.9
  • Chapter 7 समाकलन Ex 7.10
  • Chapter 7 समाकलन Ex 7.11
  • Chapter 7 समाकलन विविध प्रश्नावली

JAC Class 12 Maths Chapter 8 समाकलनों के अनुप्रयोग

  • Chapter 8 समाकलनों के अनुप्रयोग Ex 8.1
  • Chapter 8 समाकलनों के अनुप्रयोग Ex 8.2
  • Chapter 8 समाकलनों के अनुप्रयोग विविध प्रश्नावली

JAC Class 12 Maths Chapter 9 अवकल समीकरण

  • Chapter 9 अवकल समीकरण Ex 9.1
  • Chapter 9 अवकल समीकरण Ex 9.2
  • Chapter 9 अवकल समीकरण Ex 9.3
  • Chapter 9 अवकल समीकरण Ex 9.4
  • Chapter 9 अवकल समीकरण Ex 9.5
  • Chapter 9 अवकल समीकरण Ex 9.6
  • Chapter 9 अवकल समीकरण विविध प्रश्नावली

JAC Class 12 Maths Chapter 10 सदिश बीजगणित

  • Chapter 10 सदिश बीजगणित Ex 10.1
  • Chapter 10 सदिश बीजगणित Ex 10.2
  • Chapter 10 सदिश बीजगणित Ex 10.3
  • Chapter 10 सदिश बीजगणित Ex 10.4
  • Chapter 10 सदिश बीजगणित विविध प्रश्नावली

JAC Class 12 Maths Chapter 11 त्रि-विमीय ज्यामिति

  • Chapter 11 त्रिविमीय ज्यामिति Ex 11.1
  • Chapter 11 त्रिविमीय ज्यामिति Ex 11.2
  • Chapter 11 त्रिविमीय ज्यामिति Ex 11.3
  • Chapter 11 त्रिविमीय ज्यामिति विविध प्रश्नावली

JAC Class 12 Maths Chapter 12 रैखिक प्रोग्रामन

  • Chapter 12 रैखिक प्रोग्रामन Ex 12.1
  • Chapter 12 रैखिक प्रोग्रामन Ex 12.2
  • Chapter 12 रैखिक प्रोग्रामन विविध प्रश्नावली

JAC Class 12 Maths Chapter 13 प्रायिकता

  • Chapter 13 प्रायिकता Ex 13.1
  • Chapter 13 प्रायिकता Ex 13.2
  • Chapter 13 प्रायिकता Ex 13.3
  • Chapter 13 प्रायिकता Ex 13.4
  • Chapter 13 प्रायिकता Ex 13.5
  • Chapter 13 प्रायिकता विविध प्रश्नावली

JAC Class 10 Sanskrit Solutions Shemushi Bhag 2 Jharkhand Board

JAC Jharkhand Board Class 10th Sanskrit Solutions शेमुषी भाग 2

JAC Class 10 Sanskrit अपठित-अवबोधनम्

JAC Class 10 Sanskrit अनुप्रयुक्त-व्याकरणम्

JAC Class 10 Sanskrit रचनात्मक कार्यम्

JAC Class 9 Science Important Questions Chapter 15 Improvement in Food Resources

JAC Board Class 9th Science Important Questions Chapter 15 Improvement in Food Resources

Multiple Choice Questions

Question 1.
Nitrogen, phosphorus, and potassium are examples of …………….
(a) micronutrients
(b) macronutrients
(c) fertilizers
(d) both (a) and (c)
Answer:
(b) macronutrients

Question 2.
Cyprinus and Parthenium are types of …………….
(a) diseases
(b) pesticides
(c) weeds
(d) pathogens
Answer:
(c) weeds

Question 3.
Using fertilisers in farming is an example of …………… .
(a) no cost production
(b) low – cost production
(c) high – cost production
(d) none of these
Answer:
(c) high – cost production

Question 4.
What is the other name for Apis cerana indica?
(a) Indian cow
(b) Indian buffalo
(c) Indian honeybee
(d) None of these
Answer:
(c) Indian honeybee

JAC Class 9 Science Important Questions Chapter 15 Improvement in Food Resources

Question 5.
The management and production of fish is called …………… .
(a) pisciculture
(b) apiculture
(c) sericulture
(d) aquaculture
Answer:
(a) pisciculture

Question 6.
Pasturage is related to …………… .
(a) cattle
(b) fishery
(c) apiculture
(d) sericulture
Answer:
(c) apiculture

Question 7.
What is the process of growing two or more crops in a definite pattern called?
(a) Crop rotation
(b) Intercropping
(c) Mixed cropping
(d) Organic cropping
Answer:
(b) Intercropping

Question 8.
The kharif season extends from …………… .
(a) November to April
(b) June to October
(c) March to November
(d) December to March
Answer:
(b) June to October

Question 9.
For mixed cropping, which of the following combinations of crops is not suitable?
(a) Wheat + maize
(b) Wheat + gram
(c) Wheat + mustard
(d) Groundnut + sunflower
Answer:
(a) Wheat + maize

Question 10.
Catla, Rohu and Mrigals constitute …………… .
(a) marine fishes
(b) brackish water fishes
(c) fresh water fishes
(d) both (a) and (b)
Answer:
(c) fresh water fishes

Analysing & Evaluating Questions

Question 11.
Madhu visited a dairy farm with her friends. There they saw the various kinds of cattle kept in sheds, food given to them and so on. What are the main components of feed provided to the cattle?
(a) Roughage
(b) Concentrates
(c) Water
(d) All of these
Answer:
(d) All of these

Question 12.
Find out the correct sentences.
(i) Hybridisation means crossing between genetically dissimilar plants.
(ii) Cross between two varieties is called interspecific hybridisation.
(iii) Introducing genes of desired character into a plant gives genetically modified crop.
(iv) Cross between plants of two species is called intervarietal hybridisation.
(a) (i) and (iii)
(b) (ii) and (iv)
(c) (ii) and (iii)
(d) (iii) and (iv)
Answer:
(a) (i) and (iii)

Question 13.
The characteristic which is not chosen for selective breeding in dairy animals is
(a) lactation period
(b) resistance to diseases
(c) good shelter
(d) nutritional requirement
Answer:
(c) good shelter

Assertion Reason Questions

Directions: In the following questions, the Assertions and the Reasons have been put forward. Read the statements carefully and choose the correct alternative from the following:
(A) Both the assertion and the reason are correct and the reason is the correct explanation of the assertion.
(B) The assertion and the reason are correct but the reason is not the correct explanation of the assertion.
(C) The assertion is true but the reason is false.
(D) Both the statements are false.
1. Assertion: Organic matter is important for crop production.
Reason: Organic matter provides major essential nutrients to the plant.
Answer:
(C) The assertion is true but the reason is false.

2. Assertion: Manure is better than fertilisers in maintaining soil fertility.
Reason: Manure improves soil structure and increases the water holding capacity of soil.
Answer:
(A) Both the assertion and the reason are correct and the reason is the correct explanation of the assertion.

3. Assertion: It is better to grow soyabean with maize in the same field.
Reason: Root nodules of soyabean plants have nitrogen fixing bacteria which enrich the soil with nitrogen.
Answer:
(A) Both the assertion and the reason are correct and the reason is the correct explanation of the assertion.

4. Assertion: Mixed cropping is a good practice in agriculture.
Reason: By mixed cropping, number of weeds in the field can be reduced.
Answer:
(C) The assertion is true but the reason is false.

5. Assertion: Grains to be stored should have low moisture level.
Reason: Low moisture level in grains inhibits the growth of bacteria and fungi.
Answer:
(A) Both the assertion and the reason are correct and the reason is the correct explanation of the assertion.

Very Short Answer Type Questions

Question 1.
State one demerit with composite fish culture system.
Answer:
Many fishes breed only during monsoon so hormonal stimulation has to be given. Also, good quality fish seeds are not available.

Question 2.
State one importance of photoperiod in agriculture.
Answer:
Photoperiod in agriculture provides adequate light for flowering.

Question 3.
Name two micronutrients and two macronutrients which plants take from the soil.
Answer:
(a) Macronutrients are: calcium (Ca), magnesium (Mg)
(b) Micronutrients are: boron (B), chloride (Cl)

Question 4.
How does catla differ from mrigal?
Answer:
Catla belongs to genus Catla while mrigal belongs to genus Cirrhinus. Catla is a surface feeder and native to the Northern waters of India while mrigal is a bottom – feeder and native to the Ganges and Brahm putra rivers of India.

JAC Class 9 Science Important Questions Chapter 15 Improvement in Food Resources

Question 5.
Name the two vitamins which are added in the poultry feed.
Answer:
Vitamins A and K.

Question 6.
From where do plants acquire the following nutrients?
(a) Nitrogen
(b) Hydrogen
Answer:
(a) Soil (b) Water

Question 7.
Which nutrients are supplied by cereals and pulses?
Answer:
Carbohydrates and proteins are supplied by cereals and pulses, respectively.

Question 8.
Name any two weeds of crop field.
Answer:
Xanthium (chota dhatura), Parthenium (gajar ghas), Cyperinus rotundus (motha).

Question 9.
Define animal husbandry.
Answer:
Animal husbandry is the practice of management and care of farm animals by humans for profit.

Question 10.
Mention two exam pies of crop combinations that are grown in mixed cropping.
Answer:
Some combinations of mixed cropping are:
(a) Wheat and mustard
(b) Maize and urad (pulse)
(c) Groundnut and sunflower

Question 11.
(a) Name an exotic variety of honeybee grown in India.
(b) What is the rearing of fish on a large scale called?
Answer:
(a) Apis cerana indica
(b) Pisciculture

Question 12.
Name two exotic cattle breeds with long lactation periods?
Answer:
The period of milk production after the birth of a calf is called lactation period. Jersey and Brown Swiss are two exotic cattle breeds having long lactation periods.

Question 13.
Between broiler and layer, which one matures earlier?
Answer:
Broilers have fast growth rate.

Question 14.
State the difference between compost and vermicompost.
Answer:

Compost Vermicompost
The compost is obtained by decomposition of organic waste like animal excreta, plant waste, etc., naturally due to decomposition by bacteria. To fasten the process of decomposition redworms are added to the organic matter to obtain compost.

Question 15.
Name two varieties of food required for milch animals.
Answer:
(a) Food to keep animals healthy,
(b) Food to increase lactation.

Question 16.
Define apiculture.
Answer:
Keeping bee for obtaining honey commercially is called apiculture.

Question 17.
Define hybridisation.
Answer:
Hybridisation refers to crossing between genetically dissimilar plants to obtain better variety of crops.

Analysing & Evaluating Questions

Question 18.
A farmer wants to use a crop variety that can give a good yield. What should he do to select the variety to get the desired result?
Answer:
A good crop yield can be obtained by selecting varieties having useful characteristics such as disease resistance, response to fertilizers and high yields.

Question 19.
A bee – keeper tries to collect a good yield of honey from his apiaries. However, he is unable to collect adequate honey. Suggest him a way to produce more honey.
Answer:
The bee – keeper should maintain his apiaries in between the fields of flowering plants or pasturage. This will allow bees to collect plenty of nectar and pollen from the variety of flowers. Also, the taste of honey depends on the variety of flowers available to the bees.

Question 20.
A dairy farmer wants to maintain a good and clean shelter for his dairy animals. How can he do this so that his animals stay healthy and produce clean milk?
Answer:
The shelter for dairy animals should have following features.

  1. It should be well – ventilated to allow fresh air to enter.
  2. It should have leakage – proof roof to protect them from rain, heat and cold.
  3. The floor of cattle shed should be sloping for easy cleaning and keeping it dry.

Short Answer Type Questions

Question 1.
Distinguish between a mullet and a prawn.
Answer:
Mullet is a type of fish while prawn is a crustacean. Both live in water and serve as a food supplements worldwide. Prawn belongs to the phylum arthropoda, whereas mullet belongs to the group of pisces. So one can use their characteristic features to distinguish between the two.

Question 2.
What are genetically modified (GM) crops?
Answer:
GM (Genetically Modified) crops are the crops in which a gene from some other organism, like another plant or a microorganism, is inserted to get desired characteristics such as disease resistance, response to fertilisers, product quality and high yields. For example, varieties of cotton, maize, papaya, soyabean, sugar beet, squash, etc., have been modified genetically.

Question 3.
Give the technical terms for milk -producing females and farm labour animals.
Answer:
Milk – producing females are called milch animals (dairy animals), while the ones used for farm labour are called draught animals.

JAC Class 9 Science Important Questions Chapter 15 Improvement in Food Resources

Question 4.
Mention the preventive and control measures used before the grains are stored.
Answer:
Cleaning of the produce before storage, proper drying of the produce first in sunlight and then in shade, and fumigation using chemicals that can kill pests.

Question 5.
What is the effect of deficiency of nutrients?
Answer:
Deficiency of nutrients affects physiological processes in plants including reproduction, growth, susceptibility to diseases, yield, etc. General health of the plants depends on the nutrients.

Question 6.
In what way does manure help in soil fertility?
Answer:
Manure helps in enriching the soil with mainly organic matter and small quantities of nutrients. The bulk of organic matter in the form of manure helps in increasing water holding capacity in sandy soil. In clayey soil, the large quantities of organic matter help in drainage and avoiding waterlogging.

Question 7.
Give two advantages of using chemical fertilisers over manure.
Answer:
Two advantages of using chemical fertilisers over manure are as follows:

  1. Chemical fertilisers are ‘nutrient specific’ and can provide specific elements like nitrogen, phosphorus or potassium to the soil in any desired quantity. Manure is, however, not nutrient specific.
  2. Chemical fertilisers, being soluble in water, are readily absorbed by the crops. This is not so in the case of manures.

Question 8.
What is green revolution?
Answer:
Bumper production of cereals (grains) using high-yielding varieties (HYV), higher dose of fertiliser and better modes of irrigation is known as green revolution.

Question 9.
What are pesticides? Give four methods of pest control.
Answer:
Pesticides are the chemicals used to control weeds, insects, rodents, fungi and diseases of plants. They include weedicides, insecticides and fungicides. Some methods of pest control are:

  1. Use of resistant varieties
  2. Optimum time of sowing the seeds
  3. Follow crop rotation and cropping pattern
  4. Deep ploughing of the field in summers to destroy undesirable weeds and pathogens.

Question 10.
Define organic farming.
Answer:
It is the farming in which no chemical fertilisers, pesticides or herbicides are used. It uses all organic matter for the growth of plants like manure, neem leaves as pesticides during grain storage, etc.

Question 11:
What desirable traits are focused to develop hybrids by cross-breeding indigenous and exotic breeds of fowl?
Answer:
Desirable traits are focused to develop hybrids by cross-breeding indigenous and exotic breeds of fowl:

  1. Number and quality of chicks
  2. Dwarf broiler parent for commercial chick production as they require less space and food.
  3. Summer adaptation capacity a tolerance to high temperature
  4. Low maintenance requirements
  5. Reduction in the size of the layer with ability to utilise more fibrous and cheaper diets which are formulated using agricultural by – products.

Question 12.
What decides the quality and quantity of honey production in an apiary?
Answer:
The quality and quantity of honey production in an apiary:

  1. For quality of honey: The pasturage, i.e., the kind of flowers available to the bees for nectar and pollen collection will determine the taste of the honey.
  2. For quantity of honey: Variety of bee used for the collection of honey. For example, A. mellifera is used to increase yield of honey.

Analysing & Evaluating Questions

Question 13.
What would happen if poultry birds are larger in size and have no summer adaptation capacity? In order to get small-sized poultry birds having summer adaptability, what method will be employed?
Answer:
The maintenance of optimum temperature is required for better egg production in poultry farming. The large size of birds with no adaptability to high temperature may cause decline in egg production. To obtain small-size birds with high – temperature adaptability during summer season, cross – breeding of poultry birds for desired characteristics can be done. Small size is also needed for better housing and less feed.

Question 14.
Figure below shows the two crop fields (plots A and B) that have been treated by manures and chemical fertilisers respectively, keeping other environmental factors same. Observe the graph and answer the following questions:
(a) Why does plot B show sudden increase and then gradual decrease in yield?
(b) Why is the highest peak in plot A graph slightly delayed?
(c) What is the reason for the different pattern of the two graphs?
JAC Class 9th Science Solutions Chapter 15 Improvement in Food Resources. 1
Answer:
(a) The addition of chemical fertilisers initially leads to rise in crop yield because of the release of the NPK (nitrogen, phosphorus and potassium) and some other nutrients in high quantity. The gradual decline in yield, as shown in plot B, is due to the continuous use of these fertilisers, which cause killing of useful microbes in the soil and alter the chemical composition of soil.

(b) Manures supply nutrients to the soil slowly, as these contain organic matter in high amount. Therefore, manures enrich the soil with nutrients slowly and continuously for a long time. This is the reason that the highest peak in plot A is delayed but maintained for longer period.

(c) In case of plot A, it indicates that the use of manure remains beneficial for longer duration in terms of crop yield and remains high even when the quantity of manure is increased. In case of plot B, chemical fertilisers when used for longer period cause various problems. The loss of soil fertility occurs due to killing of useful microbes in the soil that reduces decomposition of organic matter.

Long Answer Type Questions

Question 1.
Name two fresh initiatives taken to save water and increase the water availability for agriculture.
Answer:
Two new irrigation systems have been developed to save water and increase the availability of water to the crops.
These are:
1. Drip irrigation system: Here, water is supplied to the roots of the plants directly in a drop wise manner. This prevents unnecessaiy wastage of water.
JAC Class 9th Science Solutions Chapter 15 Improvement in Food Resources. 2
2. Sprinkler system: Here, water is sprinkled over the crops like it happens in rain. So, water is distributed uniformly and absorbed by the soil in a better way.
JAC Class 9th Science Solutions Chapter 15 Improvement in Food Resources. 3

Question 2.
What are the factors for which variety improvement of crop is done?
Answer:
The factors for which variety improvement of crop is done are as follows:

  1. Higher yield: To increase productivity of the crop per acre.
  2. Improved quality: The quality of crop products varies from crop to crop, e.g., protein quality is important in pulses, oil quality in oilseeds, longer shelf life in fruits and vegetables.
  3. Biotic and abiotic resistance: Biotic factors are the diseases, insects and nematodes while abiotic factors are drought, salinity, water logging, heat, cold and frost which affect the crop productivity. Varieties resistant to these factors can increase the crop production.
  4. Change in maturity duration: Shorter maturity period of crop reduces the cost of crop production and makes the variety economical. Uniform maturity makes the harvesting process easy and reduces losses during harvesting.
  5. Wider adaptability: It allows the crops to be grown under different climatic conditions in different areas.
  6. Desirable agronomic characteristics: It increases productivity, (e) g., tallness and profuse branching are desirable characters for fodder crops; while dwarfness is desired in cereals, so that less nutrients are consumed by these crops.

Question 3.
Define manure. What are its three different types?
Answer:
Manure contains large quantities of organic matter and also supplies small quantities of nutrients to the soil. It is prepared by the decomposition of animal excreta and plant waste. It helps in enriching the soil with nutrients and organic matter and increasing soil fertility. On the basis of the kind of biological waste used to make manure, it can be classified into three types:

  1. Compost
  2. Vermicompost
  3. Green manure

1. Compost: It can be farm waste material such as livestock excreta (cow dung, etc.), vegetable waste, animal refuse, domestic waste, sewage, straw, eradicated weeds, etc. These materials are decomposed in pits and this process of decomposition is called composting.

2. Vermicompost: The compost which is made by the decomposition of plant and animal refuse with the help of redworms is called vermicompost.

3. Green manure: Prior to the sowing of the crop seeds, some plants like sun hemp or guar are grown and then mulched by ploughing them into the soil. These green plants thus turn into green manure which helps in enriching the soil in nitrogen and phosphorus.

JAC Class 9 Science Important Questions Chapter 15 Improvement in Food Resources

Question 4.
What are fertilisers? Excessive use of fertilisers is not advisable. Explain.
Answer:
Fertilisers are commercially produced plant nutrients. Fertilisers supply nitrogen, phosphorus and potassium to the crops. They are used to ensure good vegetative growth (leaves, branches and flowers), giving rise to healthy plants. Fertilisers are an important factor in the higher yields of high – cost farming.
Excessive use of fertilisers is not advisable as:

  1. It leads to soil and water pollution.
  2. It can destroy the fertility of soil.

As the soil is not replenished, microorganisms in the soil are harmed by fertilisers.

Question 5.
How does intercropping differ from mixed cropping?
Or
What are the different cropping systems?
Answer:
It includes different ways of growing crops so as to get the maximum benefit. These different ways include the following:
1. Mixed cropping: Mixed cropping is growing two or more crops simultaneously on the same piece of land, e.g., wheat + gram, or wheat + mustard, or groundnut + sunflower. This reduces disease risk and gives some insurance against failure of one of the crops.

2. Intercropping: It involves growing two or more crops simultaneously on the same field in a definite proportion or pattern. A few rows of one crop alternate with a few rows of the other crop, e.g., soyabean + maize, or finger millet (bajra) + cowpea (lobia). The crops are selected such that their nutrient requirements are different. This ensures maximum utilisation of the nutrients supplied and also prevents pests and diseases from spreading to all the plants belonging to one crop in a field. This way, both the crops can give better yield.

3. Crop rotation: The growing of different crops on a piece of land in a pre-planned succession is known as crop rotation. Depending upon the duration, crop rotation is done for different crop combinations. The availability of moisture and irrigation facilities decide the choice of the crop to be cultivated after one harvest. If crop rotation is done properly, two or three crops can be grown in a year with good harvest.

Question 6.
Explain the various methods of irrigation in India.
Answer:
Proper irrigation is very important for the success of crops. Different kinds of irrigation systems include wells, canals, rivers and tanks.

  1. Wells: These are of two types, viz., dug wells and tube wells. In a dug well, water is collected from water bearing strata Tube wells can tap water from the deeper strat(a) From these wells, water is lifted by pumps for irrigation.
  2. Canal system: Water from the main river or reservoir is carried by canal into the field which is divided into branch canals having further distributaries to irrigate the field.
  3. River lift system: In areas where canal flow is insufficient or irregular due to inadequate reservoir release,
    the lift system is more rational. Water is directly drawn from the rivers for supplementing irrigation in areas close to rivers,
  4. Tanks: These are small storage reservoirs which intercept and store the run-off of smaller catchment areas.

Question 7.
Describe the different types of fisheries.
Answer:
The different types of fisheries are marine fisheries, mariculture, inland fisheries, aquaculture and capture fishing.

  1. Marine fisheries: They are caught using fishing nets. Large schools of fishes are located by satellites. Some are farmed in sea water.
  2. Mariculture: They are cultured in seawater. This culture of fisheries is called mariculture.
  3. Inland fisheries: The fisheries in fresh water resources like canals, ponds, reservoirs and rivers are called inland fisheries.
  4. Aquaculture: Culture of fish done in different water bodies is called aquaculture.
  5. Capture fishing: It is the method of obtaining fishes from natural resources, both marine and fresh water.

Question 8.
List six facilities that must be provided to cattle to ensure their good health and production of clean milk.
Answer:
Following facilities must be provided to cattle:

  1. Regular brushing to remove dirt and loosen hair.
  2. Well – ventilated roofed sheds for shelter that can protect them from rain, heat and cold.
  3. The floor of the cattle shed needs to be sloping so as to keep them dry and to facilitate cleaning and spraying of disinfectants at regular intervals.
  4. A balanced diet should be given which contains:
    • roughage which provides high amount of fibre, and
    • concentrate that provides high levels of proteins and other nutrients.
  5. Certain food additives containing micronutrients that promote the health and milk output of dairy animals.
  6. Vaccinations of farm animals, at proper time, against major viral and bacterial diseases.

Analysing & Evaluating Questions

Question 9.
Meena belongs to an agricultural family. She attended a seminar of agricultural practices organised by her school. By listening to the research work of scientists, she learned that spraying pesticides on crops is very harmful for the environment. Next day, she saw the stored tanks of pesticides at her home and told her parents not to use these in excessive quantity.
1. Why are pesticides used in crop fields?
2. What are the various types of pesticides used by the farmers?
3. How can Meena convince her parents to stop using pesticides in large quantities?
4. What alternatives could Meena suggest to her parents instead of using pesticides?
Answer:

  1. The pesticides are used in fields to protect the plants from disease – causing organisms, i.e., bacteria, fungi, viruses, nematodes and mycoplasmas.
  2. Depending on the type of organisms, they destroy, pesticides can be of the following types.
    • Herbicides (for weeds)
    • Insecticides (for insects)
    • Fungicides (for fungi)
    • Bactericides (for bacteria)
  3. Meena can tell her parents that regular and excessive use of pesticides contaminates water and soil, causing pollution in the environment. The pesticides affect the quality of food and leave residues on food items which may affect the health of consumers.
  4. She could suggest the use of biological control methods or use of disease-resistant varieties of crops.

Activity 1
Visit a weed – infested field in the month of July or August and make a list of the weeds and insect pests in the field.

Observations:

  1. Do it yourself.
  2. Weeds are unwanted plants in the cultivated field, e.g., Xanthium (chota dhatura), Parthenium (gajar ghas) and Cyperinus rotundus (motha). They compete for food, space and light.
  3. Some insect pests of crop fields include aphids, blister beetles, common stalk borer, com borer, flour beetle, etc.

Activity 2
Visit a local poultry farm. Observe the types of breeds and note the type of ration, housing and lighting facilities given to them. Identify the layers and broilers.

Observations:

  1. Do it yourself and note down:
    • types of breeds of poultry: Aseel, white Leghorn, Rhode Island Red.
    • types of ration, housing and lighting facilities given to them.
  2. Identify the layers, for example, White leghorn, Rhode Island Red, and broilers, for example, Plymouth Rock or Aseel or any other.

Value Based Questions

Question 1.
A group of eco – club students made a compost pit in the school, they collected all the biodegradable waste from the school canteen and used it to prepare the compost.
1. Name two wastes that can be used for the compost and two wastes obtained from canteen which cannot be used for the compost making?
2. What is the other important component required for making the compost?
3. What values of eco – club students are reflected in this act?
Answer:
The compost:

  1. Two wastes used for compost are vegetable peels and fruit peels. Two waste materials that cannot be used as compost are polythene bags and plastic items.
  2. Bacteria and fungi present in soil are the other important component for making compost.
  3. Eco – club students reflect the value of group work and responsible citizens.

Question 2.
Large number of Bhetki fish died and got crushed in the turbines of hydroelectric power stations while
they migrated from river to sea The environmentalist gave power plant the solution of this problem. Now all Bhetki fish is removed with the help of a special technique and hence do not enter the turbines to crush and die.
1. Suggest two different varieties of fish.
2. What value of environmentalist is reflected in the above case?
Answer:
The turbines to crush and die:

  1. Two varieties of fish are bony and cartilaginous.
  2. Environmentalist showed the value of concern and caring individuals.

JAC Class 9 Science Important Questions

JAC Class 9 Science Important Questions Chapter 14 Natural Resources

JAC Board Class 9th Science Important Questions Chapter 14 Natural Resources

Multiple Choice Questions

Question 1.
Most of the water on the earth’s surface is found in
(a) lakes
(b) rivers
(c) oceans and seas
(d) underground
Answer:
(c) oceans and seas

Question 2.
Ozone hole was first observed over
(a) Antarctica
(b) Australia
(c) Arctic ocean
(d) America
Answer:
(a) Antarctica

Question 3.
Nitrogen fixing bacteria cannot fix N2 in the presence of
(a) CO2
(b) N2
(c) O2
(d) light
Answer:
(c) O2

Question 4.
Which of the following compounds is not degraded by any biological process?
(a) CFCs
(b) CH4
(c) Glucose
(d) Nitrites
Answer:
(a) CFCs

Question 5.
Nitrogen – fixing bacteria are found in the roots of
(a) wheat
(b) maize
(c) pulses
(d) sugarcane
Answer:
(c) pulses

Question 6.
Venus and Mars have no life because
(a) they have no atmosphere
(b) their atmosphere has only oxygen
(c) their atmosphere has 95% – 97% carbon dioxide
(d) their atmosphere has 95% – 97% oxygen
Answer:
(c) their atmosphere has 95%-97% carbon dioxide

Question 7.
Which one of the following organisms are very sensitive to the levels of contaminants like sulphur dioxide in air?
(a) Bacteria
(b) Fungi
(c) Algae
(d) Lichens
Answer:
(d) Lichens

JAC Class 9 Science Important Questions Chapter 14 Natural Resources

Question 8.
Burning of fossil fuels adds
(a) CO2, SO2, NO2 gases in air
(b) C, SO2, N2 gases in air
(c) O2, SO3, NO3 gases in air
(d) H2O, CO2 NO2, gases in air
Answer:
(a) CO2, SO2, NO2 gases in air

Question 9.
Nitrogen fixation can be done by
(a) Industries
(b) Rhizobium
(c) Lightening
(d) All of the above
Answer:
(d) All of the above

Question 10.
On moon the temperature ranges from – 190°C to 110°C. This is due to
(a) absence of water bodies
(b) presence of water bodies
(c) absence of biogeochemical cycles
(d) absence of atmosphere
Answer:
(d) absence of atmosphere

Question 11.
Depletion of ozone molecules in the stratosphere is due to
(a) chlorine compounds
(b) fluorine compounds
(c) halogen compounds
(d) none of these
Answer:
(c) halogen compounds

Question 12.
The life supporting zone of the earth is
(a) lithosphere
(b) hydrosphere
(c) atmosphere
(d) biosphere
Answer:
(d) biosphere

Question 13.
The organism which helps in the formation of soil is
(a) bacterium
(b) moss
(c) lichen
(d) both (b) and (c)
Answer:
(d) both (b) and (c)

Question 14.
The outermost crust of the earth is called
(a) atmosphere
(b) exosphere
(c) lithosphere
(d) hydrosphere
Answer:
(c) lithosphere

Analysing & Evaluating Questions

Question 15.
The atmosphere of the earth is heated by radiations which are mainly
(a) radiated by the sun
(b) re – radiated by land
(c) re – radiated by water
(d) re – radiated by land and water
Answer:
(c) re – radiated by water

Question 16.
The term “water pollution” can be defined in several ways. Which of the following statements does not give the correct definition?
(a) The addition of undersirable substances to water bodies
(b) The removal of desirable substances from water bodies
(c) A change in pressure of the water bodies
(d) A change in temperature of the water bodies
Answer:
(c) A change in pressure of the water bodies

Question 17.
When we breathe in air, nitrogen also goes inside along with oxygen. What is the fate of this nitrogen?
(a) It moves along with oxygen into the cells.
(b) It comes out with the CO2 during exhalation.
(c) It is absorbed only by the nasal cells.
(d) Nitrogen concentration is already more in the cells so it is not at all absorbed.
Answer:
(b) It comes out with the CO2 during exhalation.

Assertion Reason Questions

Directions: In the following questions, the Assertions and the Reasons have been put forward. Read the statements carefully and choose the correct alternative from the following:
(A) Both the assertion and the reason are correct and the reason is the correct explanation of the assertion.
(B) The assertion and the reason are correct but the reason is not the correct explanation of the assertion.
(C) The assertion is true but the reason is false.
(D) Both the statements are false.
1. Assertion: Plants cannot utilise
nitrogen directly from the atmosphere. Reason: Plants can only use nitrates and nitrites.
Answer:
(B) The assertion and the reason are correct but the reason is not the correct explanation of the assertion.

2. Assertion: Water vapour is not a greenhouse gas.
Reason: Water vapour does not contribute in global warming.
Answer:
(D) Both the statements are false.

3. Assertion: The moon has very cold and very hot temperature variations.
Reason: Moon does not possess the atmosphere.
Answer:
(A) Both the assertion and the reason are correct and the reason is the correct explanation of the assertion.

4. Assertion: It is easier to fly a kite near a sea shore.
Reason: There is a regular unidirectional wind from sea to land.
Answer:
(A) Both the assertion and the reason are correct and the reason is the correct explanation of the assertion.

5. Assertion: Legumes revive the soil fertility.
Reason: Microbes in the root nodules of legumes fix atmospheric nitrogen.
Answer:
(A) Both the assertion and the reason are correct and the reason is the correct explanation of the assertion.

Very Short Answer Type Questions

Question 1.
What is biosphere?
Answer:
The life – supporting zone of earth where atmosphere, hydrosphere and lithosphere interact and make life is known as biosphere.

Question 2.
What are the biotic and abiotic components of biosphere?
Answer:
Abiotic or physical components of biosphere consist of geographical conditions such as the temperature, rainfall, soil, seasons and the climate, while biotic components include animals, plants, fungi and bacteria.

Question 3.
What percentage of oxygen and nitrogen is present in the air?
Answer:
About 21% oxygen and 78% nitrogen is present in the air.

JAC Class 9 Science Important Questions Chapter 14 Natural Resources

Question 4.
Name the air pollutants released by the industries.
Answer:
Industrial air pollutants are sulphur dioxide, carbon dioxide, oxides of nitrogen, hydrogen sulphide, fumes of acids, dust, particles of unbumt carbon, lead, asbestos and even cement.

Question 5.
What are the two factors that cause changes in our atmosphere?
Answer:
(a) Heating of air, and
(b) formation of water vapour.

Question 6.
State any two harmful effects of air pollution.
Answer:
Two harmful effects of air pollution are:
(a) Respiratory problems
(b) Global warming

Question 7.
What is soil?
Answer:
Soil is a mixture of small particles of rocks of different sizes, humus and microscopic life.

Question 8.
State the major source of minerals in the soil.
Answer:
The mineral nutrients present in a particular soil depend on the rocks it was formed from. This means that the major source of minerals in a soil is their parent rocks.

Question 9.
What is top soil?
Answer:
The topmost layer of the soil that contains humus and living organisms in addition to the soil particles is called top soil.

Question 10.
Name two chemicals that are depleting ozone layer.
Answer:
Chlorofluorocarbons (CFCs) and halogenated ozone depleting substance (ODS).

Question 11.
Name two greenhouse gases.
Answer:
Methane and carbon dioxide.

Question 12.
Define nitrification.
Answer:
The biological conversion of ammonia into nitrites and then oxidation of nitrites to nitrates is called nitrification.

Question 13.
Name a nitrogen fixing bacterium.
Answer:
Rhizobium

Question 14.
Define humus.
Answer:
The fertile dark substance present in the topmost layer of the soil which contains dead remains of plants and animal wastes, like excreta, that adds nutrients to the soil is called humus.

Question 15.
What is denitrification?
Answer:
Conversion of nitrates into free nitrogen is called denitrification.

Question 16.
How does carbon exist in all life forms?
Answer:
Carbon is present in all life forms in the form of proteins, carbohydrates, fats, nucleic acids and vitamins.

Question 17.
Name two biologically important compounds that contain both oxygen and nitrogen.
Answer:
Proteins and nucleic acids (DNA and RNA).

Question 18.
Name the two gases given out by the burning of fossil fuels, which dissolve in rain to form acid rain.
Answer:
Sulphur dioxide (SO2) and oxides of nitrogen.

Analysing & Evaluating Questions

Question 19.
A person is burning a huge amount of waste in an open are(a) Which gas is being utilised for burning process and which gas is released into the atmosphere?
Answer:
The process of burning or combustion utilises oxygen and produces carbon dioxide. Thus, oxygen gas is being utilised in the process, and carbon dioxide is released into the atmosphere.

Question 20.
A huge amount of plant and animal waste is being dumped in a lake. What will be the condition of lake after some time?
Answer:
When organic waste (plant and animal residue) is dumped into a water body, the biological oxygen demand of the water increases. This is because the decomposition of organic matter by microorganisms needs more oxygen in water. As a result, there arises oxygen deficiency in water, which leads to the death of other aquatic organisms.

JAC Class 9 Science Important Questions Chapter 14 Natural Resources

Question 21.
Some industries release hot water or very cold water into water sources directly. Why should this be stopped?
Answer:
When excessive hot water or cold water is released into water bodies, it may affect some aquatic organisms. This is because these organisms live in a certain range of temperature and any change in this range (due to the release of excessive hot water or cold water) may cause threat to their survival.

Short Answer Type Questions

Question 1.
The atmosphere acts as a blanket. How?
Answer:
The blanket of atmosphere, which is covering the earth, keeps the average temperature of the earth fairly steady during the day and even during the course of the whole year. The atmosphere prevents the sudden increase in temperature during the daylight hours. And during the night, it slows down the escape of heat into outer space.

Question 2.
What are the consequences of global warming?
Answer:
(a) An increase in temperature of earth even by 1°C may lead to the melting of ice on the poles.
(b) The melting of ice will result in rise of sea level.
(c) Due to rise in sea level, many coastal cities will be flooded or submerged.
(d) Increase in temperature of earth results in change in weather and may cause excessive raining or drought or extreme hot or cold weather conditions.

Question 3.
Name the various organisms involved in nitrogen cycle.
Answer:
(a) Nitrogen fixing bacteria, e.g., Rhizobium, Azotobacter.
(b) Bacteria which convert complex nitrogenous organic compounds (proteins) into ammonia, e.g., Clostridium, Proteus.
(c) Nitrifying bacteria which convert ammonia into nitrates, e.g., Nitrosomonas and Nitrobacter.
(d) Denitrifying bacteria, e.g., Pseudomonas.

Question 4.
What does the presence of smog in an area indicate?
Answer:
The presence of smog in an area indicates the high percentage of smoke released in the air by combustion of fossil fuels in industries, thermal power plants or automobiles. It is an indicator of air pollution.

Question 5.
Write three ways to prevent soil pollution.
Answer:
(a) By judicious use of fertilizers and pesticides.
(b) By proper management of disposal of household waste.
(c) By practising intensive cropping and terrace farming.

Question 6.
How is greenhouse effect related to global warming?
Answer:
Higher concentration of greenhouse gases, such as carbon dioxide, methane, nitrous oxide, etc., in the atmosphere causes absorption of reflected heat and avoids their escape into the space. This phenomenon is called greenhouse effect. This leads to rise in the temperature of earth’s atmosphere throughout the world causing global warming. This global warming caused by greenhouse gases like CO2, CH4, etc., leads to the melting of glacier and polar ice. This would cause rise in the level of sea and other climate changes. Hence, we can say that global warming is a consequence of greenhouse effect.

Question 7.
What is air pollution? How is it caused? Write its two harmful effects.
Answer:
The contamination of air with unwanted gases, particles like dust, etc, which makes it unfit for inhalation is called air pollution.

  • Causes:
    1. (a) Burning of fossil fuels releases SO2, CO2 and NO2 gases.
    2. (b) Burning of fuels releases unbumt carbon particles and smoke.
    3. (c) Smoke from industries and vehicles.
  • Harmful effects:
    1. (a) It causes respiratory problems.
    2. (b) It causes allergies, asthma, cancer and heart diseases.

Question 8.
What is acid rain? Write its harmful effects.
Answer:
The gases released due to combustion of fossil fuels are SO2, NO2 and CO2. These gases remain suspended in the air. When it rains, the rainwater mixes with these gases to form sulphuric acid, nitrous acid, carbonic acid and comes down on the surface of the earth in the form of acid rain.
JAC Class 9th Science Solutions Chapter 14 Natural Resources 1
(a) It corrodes statues, monuments of marble, buildings, etc.
(b) It makes the soil acidic.
(c) It damages crops and plantations.

Question 9.
What is water pollution? Give its causes and harmful effects.
Answer:
When water is contaminated with unwanted substances and chemicals which make it unfit for use and cause diseases, it is called water pollution.

  • Causes:
    1. (a) Sewage from towns, cities is dumped in the water.
    2. (b) Fertilizers, pesticides, insecticides get washed away into the waterbodies from farmlands.
    3. (c) Effluent from industries.
  • Harmful effects:
    1. (a) Polluted water, when consumed, causes many diseases which are water – borne, like cholera, typhoid, etc.
    2. (b) Mercury in salts dumped by industries causes a brain disorder called Minamata disease.
    3. (c) Many life – forms which are susceptible to temperature changes die.

Question 10.
What is the difference between fog and smog? Give two harmful effects of smog.
Answer:
The water vapour present in air when condenses due to very low temperature is called fog. The smoke released in the air, due to burning of fuels, mixes with the fog and forms smog. Harmful effects of smog: It decreases the visibility and causes adverse effect on aeroplane landing, railways and road transport.

Question 11.
State in brief the role of photosynthesis and respiration in carbon-cycle in nature.
Answer:
Photosynthesis is performed by green plants in the presence of sunlight and it converts carbon dioxide into carbohydrates that are utilised by other living organisms through food chain. Oxygen is replenished in nature only through the process of photosynthesis. Oxygen enters the living world through the process of respiration, i.e., it oxidises the food material (glucose molecules) and produces energy and carbon dioxide.

Question 12.
Explain the importance of ozone to mankind.
Answer:
Ozone covers the earth’s atmosphere. It is present in stratosphere. It does not allow the harmful ultraviolet radiations coming from the sun to enter our earth. These ultraviolet radiations cause ionizing effect and can cause cancer and genetic disorder in any life form. The ozone is getting depleted at the South Pole near Antarctica The ozone depletion is due to the halogens like CFCs (Chlorofluorocarbons) released in the air. Chlorine and fluorine react with the ozone and split it, thereby leading to the formation of a big hole called ozone hole.

JAC Class 9 Science Important Questions Chapter 14 Natural Resources

Question 13.
How are winds caused and what decides the breeze to be gentle, strong wind or a terrible storm?
Answer:
Movement of air, terrible storm and rains, all these phenomena are the result of changes that take place in our atmosphere due to the heating of air and the formation of water vapour. Water vapour is formed due to the heating of water bodies and the activities of living organisms. The atmosphere can be heated from below by the radiation that is reflected back or re-radiated by the land or water bodies. On being heated, convection currents are set up in the air. This causes wind. The pressure gradient or the pressure difference determines the speed and intensity of wind. Larger the gradient, more is the wind speed.

Question 14.
Why is step farming common in hills?
Answer:
At hills, the rainwater flows with a very high speed which provides very less time to absorb rainwater into the soil. So, the fields contain wide steps which slow down the speed of fast flowing water. Therefore, farming fields get more chances to absorb rainwater, i.e, more water can seep into the soil for better farming. Besides this, step farming also reduces soil erosion.

Question 15.
Write the harmful effects of ozone layer depletion.
Answer:
Harmful effects of ozone layer depletion are as follows:

  1. Due to depletion of ozone layer, more ultraviolet (UV) radiation will reach the earth. UV radiation causes skin cancer, damage to eyes and immune system.
  2. UV radiation kills microorganisms, such as bacteria, even useful ones.
  3. Ozone layer depletion may lead to variation in rainfall, ecological disturbances and dwindling of good food supply.

Analysing & Evaluating Questions

Question 16.
Rashmi visited her village during summer vacations and found that there is severe shortage of water for villagers and animals.
1. Give reason of water shortage in villages.
2. Why some areas of earth suffer from the problem of water scarcity?
3. What ways can Rashmi suggest to villagers to solve the problem of water shortage?
Answer:

  1. The lack of public water supply in villages is the most prominent reason of water scarcity in villages. Villagers depend on natural sources of water which often dry up due to excessive heat during summer.
  2. The water scarcity occurs due to uneven distribution of freshwater on the earth.
  3. Rainwater harvesting is an effective way to solve the problem of water scarcity in villages as well as in cities. The rainwater can be stored in underground tanks, check dams and recharges the groundwater. This groundwater can be drawn for use at the time of shortage of water.

Question 17.
A farmer followed the practice of sowing cereal crops regularly in his field for several seasons. After sometime, he found decline in cereal production.
(a) What may be the reason for less cereal production in farmer’s field?
(b) How the farmer can increase production in his field?
Answer:
(a) Sowing a same crop regularly in the field for several seasons makes the soil deficient of certain essential nutrients.
Thus, the fertility of soil declines after sometime and the crop production becomes less.

(b) The farmer can grow leguminous crops after cereal crop. The nitrogen fixing bacteria that live in root nodules of legume crops help in replenishment of lost nitrogen in the soil by fixing atmospheric nitrogen.

Long Answer Type Questions

Question 1.
Describe the carbon – cycle in nature.
JAC Class 9th Science Solutions Chapter 14 Natural Resources 2
Answer:
All living things are made of carbon. Carbon is also a part of the oceans, air, and even rocks. Because the earth is a dynamic place, carbon does not stay still. Carbon – cycle is the series of processes by which carbon compounds are interconverted in the environment, involving the incorporation of carbon dioxide into living tissues by photosynthesis and its return to the atmosphere through respiration, the decay of dead organisms and the burning of fossil fuels.

If we see from the beginning, CO2 in the atmosphere is taken by the plants which use it to make glucose, water and oxygen. Also, direct CO2 from air forms carbonates in water which later turns into limestone. Then, these plants are eaten us and other animals, i.e., we indirectly use COus and other animals, i.e., we indirectly use CO2 present in the plants. Also, we respire CO2 back in atmosphere.

Then, organic compounds (plants / animals) form coal and petroleum, or we can say fossil fuel. And also, animal body present in the plants. Also, we respire CO2 back in atmosphere. Then, organic compounds (plants / animals) form coal and petroleum, or we can say fossil fuel. And also, animal body forms inorganic carbonates or shells. But nowadays, we bum fossil fuels too much (and also cut the trees) which is harmful. As a result, we are not getting rid of excess CO2 from our atmosphere.

Question 2.
Why is replenishment of forests necessary?
Answer:
Forests need to be replenished because of the following reasons:

  1. Rainfall: During transpiration, trees give out enormous amount of water vapour. This water vapour helps in the formation of clouds. So, if trees are cut and not replenished, the rainfall in the area will reduce.
  2. Natural rate of tree growth: Forests cannot be re – grown in a few days or months as trees take many years to grow fully. Thus, it becomes necessary to replenish the forests periodically.
  3. Soil erosion: If a large number of trees are cut, the soil becomes naked. The topsoil, which is rich in organic matter will be washed away by water or carried away by wind. Trees help in binding the soil.
  4. Carbon dioxide – oxygen balance: Forests have a very large number of trees which give out 02 and take in C02 by photosynthesis. In this way, they help in maintaining the carbon dioxide-oxygen balance in the atmosphere.
  5. Timber and fuel: Forests are the best suppliers of timber for furniture and fuel. So, for their constant supply, forests need to be replenished.

Question 3.
Draw a labelled diagram to show nitrogen cyclele in nature.
Answer:
Nitrogen exists as free nitrogen in the atmosphere. In air, N2 is about 78%. This free nitrogen is fixed into compounds of ammonia and nitrates. Most of the organisms cannot utilise molecular nitrogen. Fixation of Nitrogen:
Fixation of free nitrogen into compounds takes place by the following means:
1. Certain blue green algae and bacteria can fix atmospheric nitrogen.

2. Nitrogen – fixing bacteria found in the root nodules of legumes such as grams, beans, pulses, etc., fix atmospheric nitrogen into nitrogen containing compounds.

3. Lightning also helps in the formation of nitrogen containing compounds. Nitrogen containing fertilisers produced artificially in factories are the fixed form of nitrogen. Plants take up compounds containing nitrogen from the soil. From plants nitrogen passes into food web Decay of dead plants and animals and excreta like urine, faeces, cause return of nitrogen compounds to the soil. Denitrifying bacteria and fire cause liberation of free nitrogen in the atmosphere.
JAC Class 9th Science Solutions Chapter 14 Natural Resources 3
Importance of Nitrogen – cycle: Nitrogen is an important constituent of tissues, proteins, enzymes, nucleic acids and amino acids. Atmosphere contains about 78 per cent nitrogen but plants and animals cannot use nitrogen in this form. Plants take nitrogen in the form of nitrates, the usable form. From plants, nitrogen travels to animals through food. If nitrogen in the form of proteins, amino acids, enzymes, etc., remains locked up in the bodies of organisms, there will be shortage of usable form of nitrogen. Therefore, circulation of nitrogen in nature is very essential.

Question 4.
Explain the oxygen – cycle in nature.
Answer:
Oxygen is an important component of everyday life. We cannot survive without oxygen. It comprises about 21% of atmospheric air. It is a component of several biological molecules such as carbohydrates, proteins, nucleic acids and fats. Like carbon dioxide, oxygen too is cycled through the process of photosynthesis and respiration. Oxygen is also utilised during combustion or burning.
JAC Class 9th Science Solutions Chapter 14 Natural Resources 4
Oxygen – cycle: Oxygen from the atmosphere is used up in three processes, viz., combustion, respiration and in the formation of oxides of nitrogen.

  1. Animals take in oxygen through the process of respiration. They release CO2 into the atmosphere.
  2. Carbon dioxide, released by animals, is used by plants in the process of photosynthesis.
  3. Plants release oxygen into the atmosphere as a by-product of photosynthesis.
  4. Fuels need oxygen for combustion, so they take oxygen and release CO2 into the atmosphere as a by-product along with other gases.
  5. CO2 is released into the air in the process of decaying of dead animals and plants.
  6. This CO2 is taken up by plants for the process of photosynthesis and O2 is released and this process continues.

Question 5.
Describe water – cycle.
Answer:
Water is one of the most important physical components which is essential for survival of life on the earth. The water from the water bodies on evaporation moves up. As the vapours rise up in the atmosphere they become cooler and condense to form clouds which fall down as rain. Rainwater then passes through rivers and gets collected again in the ocean. The circulation of water in this manner is known as water – cycle. The cycle is also performed by living beings like absorption and transpiration of water by plants and drinking by animals. Animals lose water during respiration and perspiration. They lose water through excretion also.
JAC Class 9th Science Solutions Chapter 14 Natural Resources 5

Analysing & Evaluating Questions

Question 6.
There are several sources like respiration by living organisms, combustion, burning of fossil fuels and forest fires which contribute immensely in the carbon dioxide levels of atmosphere. Despite all these activities, the air contains only a mere fraction of carbon dioxide in it. How does it happen?
Answer:
The level of carbon dioxide does not increase in atmosphere because atmospheric carbon dioxide is fixed continuously in different components by the following ways.

  • The plants ‘fix’ or capture the carbon dioxide and convert it into glucose through the process known as photosynthesis.
  • Animals get their carbon directly by eating plants or indirectly by eating herbivores. Many marine animals use carbonates dissolved in seawater to make their shells.
  • The fossil fuels are also the storehouse of carbon. These are the deposits of organic materials formed from decayed plants and animals deep inside the earth. By exposure to heat and pressure in the earth’s crust over hundreds of millions of years, these dead decaying organisms changed into fossil fuels, such as coal and petroleum.
  • The water rich in carbon dioxide accumulates at the bottom of water bodies and forms limestone or carbonated rocks. It involves a series of chemical reactions that remove carbon dioxide from the atmosphere and deposits it in the form of rocks.

Activity 1

  • Take the following:
    1. (i) a beaker full of water
    2. (ii) a beaker full of soil/sand and
    3. (iii) a closed bottle containing a thermometer.
  • Measure the temperature of all these in shade.
  • Now, keep them in bright sunlight for three hours and measure the temperature of all three vessels.

Observations:

  • The temperature of air is less in shade than the temperature of sand or water.
  • The temperature of water does not rise quickly whereas sand gets heated up easily.
  • The temperature of air in the closed bottle is more than the temperature of air in open. This is because heat received from the sun has no outlet to reflect back the heat radiation. The glass does not allow to escape reflected heat radiations to go out.

Activity 2

  • Place a candle in a beaker or wide mouthed bottle and light it. Light an incense stick and take it to the mouth of the beaker as shown in the figure.
  • Now, keep the incense stick near the edge of the mouth, a little above the candle, and in other regions. Record your observations.

Observations:

  • When the incense stick is kept near the edge of the mouth, the smoke flows inwards towards the flame. The hot air around the candle rises up and cold air from the surroundings rushes in to fill the space. This air rushing inside the beaker brings smoke towards the flame.
  • The smoke rises up along with hot rising air when incense stick is kept a little above the candle.
  • In other places, the smoke from the incense stick rises up and then diffuses in the air.

Activity 3
Take two identical trays and fill them with soil. Plant mustard or green gram or paddy in one of the trays and water both the trays regularly for a few days, till the first tray is covered with plant growth. Now, tilt both the trays and fix them in that position. Make sure that both the trays are tilted at the same angle. Pour equal amount of water gently on both trays such that the water flows out of the trays.
JAC Class 9th Science Solutions Chapter 14 Natural Resources 6
1. Study the amount of soil that is carried out of the trays by the water.
2. Now pour equal amounts of water on both the trays from a height. Pour three or four times the amount that you poured earlier.
3. Study the amount of soil that is carried out of the trays now. Record your observations.

Observations:

  • The tray without vegetation loses more soil and holds more water than the tray that has plants.
  • On pouring water on both the trays from a height, more soil flows along with water in the tray without vegetation.
  • Less amount of soil is washed out earlier than that washed out when water was poured from a height.

Value Based Questions

Question 1.
Sudha saw a child sleeping in a car parked, with closed doors and glasses rolled up, in an open area on a sunny day near the market. She immediately raised an alarm and with the help of police she got the window rolled down.
1. Why was it not safe to keep the doors with window glasses rolled up for a child inside the car?
2. Name two gases that can lead to the above effect.
3. What value of Sudha is reflected in the above act?
Answer:

  1. It was not safe for the child in the car with locked doors and windows rolled up because the sunlight would result in the greenhouse effect in the car. This would increase the temperature in the car and also result in the increase in CO2 level which would lead to suffocation.
  2. Carbon dioxide gas and methane gas can lead to greenhouse effect.
  3. Sudha reflects the value of an aware citizen and responsible behaviour.

JAC Class 9 Science Important Questions Chapter 14 Natural Resources

Question 2.
After doing a project on “save water”, Sumit realised the problem of shortage of drinking water on the earth. Sumit started checking the misuse of water in his vicinity.
1. What is the percentage of drinking water available on the earth?
2. Give any two practices that one should follow to save water.
3. What value of Sumit is reflected in this act?
Answer:

  1. 1% of drinking water is available on the earth.
  2. To save water:
    • Do not use shower to take bath every day, instead use a bucket of water.
    • Mop the floor instead of washing.
    • Sumit showed the value of responsible behaviour and participating citizen.
  3. A project on “save water”, Sumit realised the problem of shortage of drinking water on the earth.

JAC Class 9 Science Important Questions

JAC Class 9 Science Important Questions Chapter 13 Why Do We Fall Ill

JAC Board Class 9th Science Important Questions Chapter 13 Why Do We Fall Ill

Multiple Choice Questions

Question 1.
The disease that affects our lungs is
(a) jaundice
(b) tuberculosis
(c) scabies
(d) herpes
Answer:
(b) tuberculosis

Question 2.
The BCG vaccine provides immunity against
(a) dengue
(b) influenza
(c) ebola
(d) tuberculosis
Answer:
(d) tuberculosis

JAC Class 9 Science Important Questions Chapter 13 Why Do We Fall Ill

Question 3.
Malaria is caused by
(a) Anopheles mosquito
(b) Bacteria
(c) Protozoa
(d) Virus
Answer:
(a) Anopheles mosquito

Question 4.
Trypanosoma, Leishmania and Plasmodium are the examples of
(a) protozoa
(b) worms
(c) fleas
(d) viruses
Answer:
(a) protozoa

Question 5.
Diarrhoea, cholera, typhoid are the diseases that have one thing in common, which is
(a) all of them are air-borne
(b) all of them are caused by a virus
(c) all of them are caused by contaminated food and water
(d) all of them cause headache
Answer:
(c) all of them are caused by contaminated food and water

Question 6.
HIV virus attacks which one of the following cells in our body?
(a) Liver cells
(b) Neurons
(c) Nephrons
(d) White blood cells
Answer:
(d) White blood cells

Question 7.
Pathogens of disease are
(a) viruses
(b) bacteria
(c) protozoa
(d) all of the above
Answer:
(d) all of the above

Question 8.
Which of the following is a worm – caused disease?
(a) Herpes
(b) Filariasis
(c) Rabies
(d) Conjunctivitis
Answer:
(b) Filariasis

Question 9.
Which of the following is not a viral disease?
(a) AIDS
(b) Rabies
(c) Polio
(d) Tuberculosis
Answer:
(b) Rabies
(d) Tuberculosis

JAC Class 9 Science Important Questions Chapter 13 Why Do We Fall Ill

Question 10.
Which of the following is caused by Plasmodium parasite?
(a) Hepatitis
(b) Jaundice
(c) Tuberculosis
(d) Malaria
Answer:
(d) Malaria

Analysing & Evaluating Questions

Question 11.
If you live in an overcrowded and poorly ventilated house, you may probably suffer from which of the following diseases?
(a) Cancer
(b) AIDS
(c) Air-borne diseases
(d) Cholera
Answer:
(c) Air – borne diseases

Question 12.
During infection or injuries, inflammation of body organs occurs due to the activation of
(a) nerves
(b) muscles
(c) immune system
(d) breathing
Answer:
(c) immune system

Question 13.
Suppose you are experiencing the symptoms of cough and breathlessness. Which organ of your body do you think might be affected?
(a) Kidney
(b) Lung
(c) Heart
(d) Stomach
Answer:
(b) Lung

Assertion-Reason Questions

Directions. In the following questions, the Assertions and the Reasons have been put forward. Read the statements carefully and choose the correct alternative from the following.
(A) Both the assertion and the reason are correct and the reason is the correct explanation of the assertion.
(B) The assertion and the reason are correct but the reason is not the correct explanation of the assertion.
(C) The assertion is true but the reason is false.
(A) Both the assertion and the reason are correct and the reason is the correct explanation of the assertion.

1. Assertion: DPT is a triple antigen.
Reason: DPT is administered against three diseases namely diphtheria, pertussis and tetanus.
Answer:
(A) Both the assertion and the reason are correct and the reason is the correct explanation of the assertion.

2. Assertion: Antibiotics are effective against both the bacteria and the viruses.
Reason:  Viruses have many biochemical mechanisms of their own.
Answer:
(A) Both the assertion and the reason are correct and the reason is the correct explanation of the assertion.

3. Assertion: Male Anopheles mosquitoes do not spread malaria.
Reason: Male Anopheles mosquitoes do not feed on human blood.
Answer:
(A) Both the assertion and the reason are correct and the reason is the correct explanation of the assertion.

4. Assertion: Typhoid spreads through contaminated food and water.
Reason: Typhoid can never become an epidemic in a locality.
Answer:
(C) The assertion is true but the reason is false.

5. Assertion: HIV attacks the immune system of a person.
Reason: HIV is responsible for AIDS in people infected with it.
Answer:
(B) The assertion and the reason are correct but the reason is not the correct explanation of the assertion.

Very Short Answer Type Questions

Question 1.
What do you understand by symptoms of a disease?
Answer:
Symptoms are the signs of a disease which indicate the presence of that particular disease.

Question 2.
What are acute diseases?
Answer:
Acute diseases are diseases that last for a very short period of time.

Question 3.
What are chronic diseases?
Answer:
Chronic diseases are diseases that last for a very long period of time.

Question 4.
What are infectious diseases?
Answer:
Infectious diseases are diseases that can spread from an infected person to another healthy person, e. g., ebola.

Question 5.
Name any one disease caused due to genetic abnormality.
Answer:
Sickle-cell anaemia.

Question 6.
Name two diseases caused by protozoa.
Answer:
Trichomoniasis and malaria.

JAC Class 9 Science Important Questions Chapter 13 Why Do We Fall Ill

Question 7.
Name two diseases each caused by bacteria, viruses and fungi.
Answer:
Bacteria – typhoid, cholera; Viruses – ebola, mumps; Fungi – Jock-itch, ringworm.

Question 8.
Write the full form of AIDS.
Answer:
Acquired Immunodeficiency Syndrome.

Question 9.
Which organism causes sleeping sickness?
Answer:
A protozoan called Trypanosoma causes sleeping sickness.

Question 10.
Name the causative agent of kala – azar?
Answer:
Leishmania.

Question 11.
Name two air-borne diseases.
Answer:
Anthrax and smallpox.

Question 12.
Name two organ specific diseases.
Answer:
Autoimmune hepatitis which affects the liver and Grave’s disease which affects the thyroid.

Question 13.
Which virus is responsible for AIDS?
Answer:
HIV virus is responsible for AIDS.

Question 14.
State the organs affected by the following diseases. jaundice, malaria, typhoid.
Answer:
Jaundice: liver; malaria – liver and RBCs; typhoid – infects the blood.

Question 15.
How do we kill microbes that enter our bodies?
Answer:
We kill disease: causing microbes with the help of medicines that block the synthesis pathways of microbes.

Question 16.
What are disease specific means of prevention?
Answer:
Disease specific means of prevention is the use of vaccine which prevents specific diseases from affecting us, e.g., tetanus vaccine, rabies vaccine, etc.

Question 17.
Why is the creation of antiviral drugs hard?
Answer:
Viruses grow inside the host and use the host cell machinery and pathways for all its biological processes. Hence, antibiotics are not able to target the virus-specific pathways. Moreover, viruses can alter their mechanisms at a very high rate, so it becomes difficult to target a specific mechanism.

Analysing & Evaluating Questions

Question 18.
Suppose your friend is suffering from severe cold and it makes him sneeze frequently heavily. What would you suggest him as a precautionary measure so that you do not become infected with the disease?
Answer:
Severe cold or cough are airborne diseases which spread through inhalation of respiratory droplets that are released by sneezing and coughing by an infected individual. Therefore, I would suggest my friend to cover his mouth while sneezing or coughing so that virus responsible for causing this disease does not infect others.

Question 19.
A person is suffering from fever and headache from quite a period of time. He is suspecting that it may be typhoid. What should he do to confirm whether it is the same disease?
Answer:
Confirmation of a particular disease can be done by undergoing proper medical check up and laboratory tests under the supervision of a doctor.

Question 20.
Suppose a person is suffering from jaundice. Whether prescribing him penicillin will be useful or not? Name the target organ for jaundice.
Answer:
No, penicillin would not be useful in the treatment of jaundice because it is a viral diseases. Target organ for jaundice is liver.

Short Answer Type Questions

Question 1.
Define health, disease, pathogens and antibiotics.
Answer:
Health. It is a state of mental, physical and social well-being.
Disease. It is the deviation from the normal healthy well-being of an individual.
Pathogens. They are disease-causing microbes, e.g., bacteria, worms, fungi, etc.
Antibiotics. These are drugs that block the biochemical pathways important to bacteria, thereby killing them.

Question 2.
What are the two main causes of a disease?
Answer:
The two main causes are immediate and contributory causes. Immediate cause-this is due to pathogens entering our bodies. Contributory cause-these are the secondary factors which allow these pathogens to enter our bodies through dirty water, contaminated food, infected surroundings, etc.

Question 3.
Define and give examples of vaccines.
Answer:
Vaccine is an antigenic substance prepared from the agent causing the disease, which is given in advance to a body to provide immunity against that specific disease, e.g., chickenpox vaccine, hepatitis vaccine, polio vaccine.

Question 4.
What is antibiotic penicillin? Give its function.
Answer:
Penicillin is a drug prepared from the fungus Penicillium, which does not allow bacteria to build its protective cell wall, thus it dies off easily. It is used to cure diseases and infections caused by bacteria.

Question 5.
A bacterium is a cell which is destroyed by an antibiotic. Our body is also made up of cells. How come antibiotics do not affect our bodies as well?
Answer:
An antibiotic blocks the biochemical pathway through which bacteria build a protective cell wall. Human body cells do not have this cell wall, so antibiotics cannot have any such effect on our body.

JAC Class 9 Science Important Questions Chapter 13 Why Do We Fall Ill

Question 6.
How can cholera become an epidemic in a locality?
Answer:
Cholera is a communicable disease that spreads through contaminated water and food. Let’s say, a person living in a locality contaminates the local water supply with cholera through his excreta. Now, all the people of that locality who drink that water will get infected with cholera.

Question 7.
Why are sick patients asked to take bed rest?
Answer:
Sick patients are asked to take bed rest so that they can conserve their energy which can be used to heal their recovering organs. Moreover, if they move around, there are higher chances of them getting infected with other diseases as their immune system is already weak.

Question 8.
Write a short note on malaria, its symptoms and control.
Answer:
Malaria is caused by a protozoan that lives in blood. The parasite enters our bodies when a female Anopheles mosquito, having the protozoa named Plasmodium, sucks our blood. This protozoan affects our liver and blood cells.

  • Symptoms: muscular pain, headache and very high fever.
  • Control: keeping the surroundings clean with no stagnant water, using mosquito repellents, use of quinine drug.

Question 9.
What is AIDS? How does a person contract AIDS?
Answer:
AIDS or Acquired Immunodeficiency Syndrome is a disease caused by the Human immuno deficiency virus. A person with AIDS has severely affected immune system. Hence, he or she dies from other diseases that thrive from the lack of Acquired WBCs in the HIV infected body.
A person contracts AIDS in the following ways:

  1. Blood transfusion
  2. Sexual intercourse
  3. From infected mother to a baby (in the womb)
  4. Sharing of needles with infected people
  5. Breast feeding (if the feeder is infected).

Question 10.
Becoming infected by an infectious microbe does not always develop into a disease. Why?
Answer:
This is because our immune system is always active and when foreign particles (microbes) enter our body, the immune system instantly attacks it, trying to kill it. So, in cases where our immune system is successful in killing the infectious microbe, we don’t develop the disease it was supposed to cause.

Question 11.
(a) Why is a balanced diet necessary for maintaining a healthy body?
(b) Name two diseases caused by junk food.
Answer:
(a) A balanced diet provides all the nutrients required by our body in the correct amount. It helps to keep our immune system healthy,

(b) Two diseases caused by junk food are obesity and high blood pressure.

Analysing & Evaluating Questions

Question 12.
No polio cases have been reported from India since the last three years. On that basis, WHO has presented certification of poliofree status to India.
1. Which pathogen is responsible for causing polio in children?
2. How the principle of immunisation is implemented for eliminating polio?
3. What is OPV?
Answer:

  1. Poliomyelitis virus.
  2. Oral vaccines for polio are given periodically to children under five years to age to eliminate the occurrence of the disease. These vaccines are the preparations of weak forms of polio virus strains. These preparations stimulate the body to produce antibodies in response to the exposure to polio viruses. Thus, body becomes immune to the polio disease.
  3. Oral Polio Vaccine.

Question 13.
Sachin’s younger brother was suffering from diarrhoea and vomiting. So he made Oral Rehydration Solution (ORS) and gave it to his brother to drink frequently. Then he thought to take him to the doctor for medical checkup.
1. What may be the cause of diarrhoea and vomiting?
2. Name the causative agents for these diseases?
3. Why Sachin gave ORS to his brother?
Answer:

  1. Diarrhoea and vomiting may occur due to the consumption of contaminated food and water.
  2. The causative agents for these are mainly bacteria, but some protozoa and viruses can also cause diarrhoea and vomiting.
  3. Due to diarrhoea and vomiting, the body loses excess of water and other salts leading to dehydration of the body. Therefore, Sachin used his knowledge to save his brother from the discomfort of dehydration by giving him ORS.

Long Answer Type Questions

Question 1.
If someone in the family gets an infectious disease, what precautionary steps will you take to help that person recover fast and prevent other family members from getting infected?
Answer:
(a) The infected person should be kept isolated in a separate room.
(b) The surroundings and the house need to be kept clean.
(c) His (the patient) clothes and utensils should be sanitised regularly.
(d) Separate towels, sheets and blankets should be used by the patient.
(e) Clean and boiled drinking water should be given to the patient.
(f) A balanced and nutritious meal should be provided to the patient.
(g) The patient should be allowed enough rest to recover fully.

Question 2.
What are the different methods used for the treatment and prevention of diseases?
Answer:
Principles of treatment for diseases are:
(a) To reduce the symptoms of the disease.
(b) To kill the cause of the disease, i.e., to kill the disease-causing microbes like bacteria, fungi, protozoa.

Principles of prevention are:
(a) General ways: It relates to preventing exposure to the microbes, which can be done in the following ways.

  1. For air – borne infections. Avoid public spaces, cover your nose while coughing and sneezing.
  2. For water – borne infections. Drink safe and filtered water.
  3. For vector – borne diseases. Keep the surroundings clean, cover your food and water, do not allow stagnant water to collect.
  4. Self – immunity. Exercise regularly to keep your immune system strong.

(b) Specific ways: By getting vaccination, regular checkups and medications.

JAC Class 9 Science Important Questions Chapter 13 Why Do We Fall Ill

Question 3.
State the mode of transmission for the following diseases. malaria, AIDS, jaundice, typhoid, cholera, rabies, tuberculosis, diarrhoea, hepatitis, influenza.
Answer:

Disease Mode of transmission
1. Malaria Mosquito bite (female Anopheles mosquito)
2. AIDS Infected blood, semen, mother’s milk, sharing needle of an infected person
3. Jaundice Contaminated water
4. Typhoid Contaminated food and water
5. Cholera Contaminated food and water
6. Rabies Bite of a rabid animal
7. Tuberculosis Cough and sneeze droplets
8. Diarrhoea Contaminated food and water
9. Hepatitis Contaminated food and water
10. Influenza Cough and sneeze droplets

Question 4.
(a) What causes chickenpox?
(b) State a few precautionary measures for it.
Answer:
(a) Chickenpox is caused by a virus called varicella-zoster virus,
(b) Some precautionary steps for chicken pox are.

  • The infected person should avoid direct contact with people.
  • His clothes should be soaked in boiling water before washing so as to kill the virus.
  • Vaccination should be taken in advance to prevent the disease.

Analysing & Evaluating Questions

Question 5.
Children living in slum areas frequently suffer from symptoms such as abdominal pain, diarrhoea, loose motions, vomiting and loss of appetite.
(a) Name the target organ or organ system for the occurrence of these symptoms.
(b) Why children are frequently suffering from these symptoms?
(c) What should be done to improve the health status of these children?
Answer:
(a) The target organ or organ system for the occurrence of these symptoms is alimentary canal.

(b) These symptoms appear frequently in the children because they live in unhygienic environment where there is non availability of clean drinking water. Hence, making them prone to infections of alimentary canal.

(c) The local authorities responsible for providing public health services should be informed regarding these health problems in the children. There should be provision of clean drinking water supply and proper sanitation in the area, so that the spread of water-borne infections can be prevented.

Activity 1

  • Find out what provisions are made by your local authority (Panchayat/ Municipal Corporation) for the supply of clean drinking water.
  • Find out if all the people in your locality are able to access this.

Observations:

  • Local authority, i.e., Municipal Corporation of our area recycles the water. Used water is treated in water treatment plants, chlorinated and supplied through pipes to people. Water taken from river is also cleaned and made potable.
  • People, who live outside municipal limits use underground water, which is supposed to be safe, by drawing water through handpumps, wells and tube-wells.

Activity 2

  • Rabies virus is spread by the bite of infected dogs and other animals. There are anti-rabies vaccines for both humans and animals.
  • Find out the plan of your local authority for the control of rabies in your neighbourhood. Also find if these measures are adequate or not. Suggest some improvements.

Observations:

  • Local authorities have plan to provide free anti-rabies vaccination at health centres, dispensaries, etc., and also catch the stray dogs. But animal loving organisations force to let them free. Pet owners are required to get anti-rabies vaccination to their dogs/ cats. But this rule is not strictly followed.
  • Suggestions.
    • People should be educated through campaigns about anti-rabies vaccination for both humans and animals.
    • Stray dogs/cats/other animals should be provided with anti-rabies vaccination.
    • Pet owners should be strictly instructed to get themselves and their pets vaccinated against rabies.

Value Based Questions

Question 1.
Radha’s brother, who is 5 years old, had high fever for two days. Doctor prescribes him antibiotics. Radha hesitantly asks for the name of the disease his brother had and why he was advised to take antibiotics without any diagnosis.
1.  Is fever a disease?
2. What is the role of antibiotics?
3. What values of Radha are reflected in the above act?
Answer:

  1. Fever is not a disease; it is a symptom.
  2. Antibiotics are medicines advised to be taken only when the immune system of a patient is unable to fight against the microbes.
  3. Radha showed moral responsibility and general awareness.

Question 2.
Jyoti was suffering from chickenpox and was advised to stay at home by her doctor. Jyoti’s friend persuades her to go for class picnic along with her and have fun. But Jyoti refuses and stays at home.
1. What is the cause of chickenpox?
2. Give one precaution for it.
3. What value of Jyoti is reflected in not going for picnic?
Answer:

  1. Virus causes chickenpox.
  2. One precaution for avoiding spread of chickenpox is to stay away from public places when one is suffering from it and take vaccination.
  3. Jyoti showed moral responsibility and self-awareness.

JAC Class 9 Science Important Questions

JAC Class 9 Science Important Questions Chapter 12 Sound

JAC Board Class 9th Science Important Questions Chapter 12 Sound

Multiple Choice Questions

Question 1.
Which part of the human ear converts sound vibrations into electrical signals?
(a) Malleus
(b) Incus
(c) Tympanic membrane
(d) Cochlea
Answer:
(d) Cochlea

Question 2.
What do dolphins, bats, and tortoises use to hear the sound?
(a) Ultrasound
(b) Infrasound
(c) Both (a) and (b)
(d) None of these
Answer:
(a) Ultrasound

Question 3.
Children under the age of 5 can hear upto
(a) 25 Hz
(b) 25 kHz
(c) 20 Hz
(d) 20 kHz
Answer:
(b) 25 kHz

JAC Class 9 Science Important Questions Chapter 12 Sound

Question 4.
Multiple reflections of sound are used in
(a) stethoscope
(b) trumpet
(c) megaphone
(d) all of these
Answer:
(d) all of these

Question 5.
To hear a distinct echo, the time interval between the original sound and the reflected sound must be at least
(a) 0.2s
(b) 1s
(c) 2s
(d) 0.1s
Answer:
(d) 0.1s

Question 6.
Speed (v), wavelength (l) and the frequency (v) of a sound wave are related as
(a) λ = v × λ
(b) v = λ – v
(c) v = λ × v
(d) v = λ/v
Answer:
(c) v = λ × v

Question 7.
Speed of sound depends upon
(a) temperature of the medium
(b) density of the medium
(c) temperature of source producing sound
(d) temperature and density of the medium
Answer:
(d) temperature and density of the medium

Question 8.
Using which characteristic of sound can we distinguish between the sounds having same pitch and loudness?
(a) Tone
(b) Note
(c) Pitch
(d) Timber
Answer:
(d) Timber

Question 9.
Loud sound can travel a larger distance, due to
(a) higher amplitude
(b) higher energy
(c) higher frequency
(d) higher speed
Answer:
(a) higher amplitude

Question 10.
A wave in slinky travelled to and fro in 5 s. The length of the slinky is 5 m. What is the velocity of the wave?
(a) 10 m/s
(b) 5 m/s
(c) 2 m/s
(d) 25 m/s
Answer:
(b) 5 m/s

Question 11.
The reciprocal of frequency is
(a) amplitude
(b) wavelength
(c) time – period
(d) wave velocity
Answer:
(c) time – period

Question 12.
To and fro motion of an object is called
(a) wave
(b) vibrations
(c) amplitude
(d) all of the above
Answer:
(b) vibrations

Question 13.
Which of the following frequencies will be audible to the human ear?
(a) 5 Hz
(b) 5000 Hz
(c) 27000 Hz
(d) 50000 Hz
Answer:
(b) 5000 Hz

Question 14.
If the distance between a crest and its consecutive trough is L, then the wavelength of the wave is given by
(a) L
(b) 2L
(c) L/2
(d) 4L
Answer:
(b) 2L

Question 15.
What is the nature of the ocean waves in deep water?
(a) Transverse
(b) Longitudinal
(c) Both transverse and longitudinal
(d) None of these
Answer:
(c) Both transverse and longitudinal

Analysing & Evaluating Questions

Question 16.
A key of a mechanical piano is struck gently and then struck again but much harder this time. In the second case
(a) sound will be louder but pitch will not be different
(b) sound will be louder and pitch will also be higher
(c) sound will be louder but pitch will be lower
(d) both loudness and pitch will remain unaffected
Answer:
(a) sound will be louder but pitch will not be different

JAC Class 9 Science Important Questions Chapter 12 Sound

Question 17.
Which kind of sound is produced by an earthquake before the main shock wave begins?
(a) ultrasound
(b) infrasound
(c) audible sound
(d) none of these
Answer:
(b) infrasound

Question 18.
Before playing the orchestra in a musical concert, a sitarist tries to adjust the tension and pluck the string suitably. By doing so, he is adjusting
(a) intensity of sound only
(b) amplitude of sound only
(c) frequency of the sitar string with the frequency of other musical instruments
(d) loudness of sound
Answer:
(c) frequency of the sitar string with the frequency of other musical instruments

Assertion Reason Questions

Directions: In the following questions, the Assertions and the Reasons have been put forward. Read the statements carefully and choose the correct alternative from the following:
(A) Both the assertion and the reason are correct and the reason is the correct explanation of the assertion.
(B) The assertion and the reason are correct but the reason is not the correct explanation of the assertion.
(C) The assertion is true but the reason is false.
(D) Both the statements are false.
1. Assertion:
Sound travels as a longitudinal wave in air.
Reason: Sound wave needs a medium for its propagation.
Answer:
(B) The assertion and the reason are correct but the reason is not the correct explanation of the assertion.

2. Assertion: Speed of sound increases on increasing the temperature of the medium through which its propagates.
Reason: On increasing the temperature, kinetic energy of the particles of medium increases.
Answer:
(B) The assertion and the reason are correct but the reason is not the correct explanation of the assertion.

3. Assertion: Stage of an auditorium has a curved sound board behind the stage.
Reason: Curved wall spreads sound in all directions evenly.
Answer:
(A) Both the assertion and the reason are correct and the reason is the correct explanation of the assertion.

4. Assertion: Sound travels faster in solids than in liquids.
Reason: Particles of solids are closely packed as compared to those of liquids.
Answer:
(A) Both the assertion and the reason are correct and the reason is the correct explanation of the assertion.

5. Assertion: Pitch of a sound wave depends on its frequency.
Reason: Higher the frequency, lesser is the pitch of the sound wave.
Answer:
(C) The assertion is true but the reason is false.

Very Short Answer Type Questions

Question 1.
What is SONAR?
Answer:
SONAR (Sound Navigation And Ranging) is a technique used for determining water depth and locating underwater objects, such as reefs, submarines and school of fish.

Question 2.
Define one hertz.
Answer:
One hertz is one vibration per second.

Question 3.
Name the two types of mechanical waves.
Answer:
The two types of mechanical waves are:

  1. Transverse wave
  2. Longitudinal wave

Question 4.
What is a wave?
Answer:
A wave is a disturbance that travels in a medium due to repeated periodic motion of particles about their mean position, such that the disturbance is handed over from one particle to the other without the actual movement of the particles of the medium.

Question 5.
What is a longitudinal wave?
Answer:
It is a wave in which the particles of the medium vibrate in the direction of propagation of the wave.

Question 6.
What is a transverse wave?
Answer:
It is a wave in which the particles of the medium vibrate perpendicular to the direction of propagation of the wave.

Question 7.
What do you understand by the term ‘echo’?
Answer:
The sound heard after reflection from a rigid obstacle back to the listener is called ‘echo’.

Question 8.
What is ‘pitch’?
Answer:
The way our brain interprets the frequency of an emitted sound is called ‘pitch’.

Question 9.
What is ‘note’ of a sound?
Answer:
The sound produced due to a mixture of several frequencies is called a ‘note’.

Question 10.
What are ‘ultrasonic’ and ‘infrasonic’ sound waves?
Answer:
Sound waves with frequencies below the audible range (less than 20 Hz) are termed as ‘infrasonic sound waves’ and sound waves with frequencies above the audible range (more than 20,000 Hz) are termed as ‘ultrasonic sound waves’.

Analysing & Evaluating Questions

Question 11.
The speed of sound in vulcanised rubber is much lower than in the common solids. Give a proper explanation.
Answer:
Rubber is soft, porous and sound absorber.

Question 12.
A sound wave corresponds to larger number of compressions and rarefaction passing through a fixed point per unit of time. Should it have higher pitch or lower pitch?
Answer:
Such a sound wave will have higher pitch, (i.e., higher frequency).

Question 13.
An echo is heard on a day when temperature is about 22°C. Will the echo be heard sooner or later if the temperature falls to 4°C?
Answer:
At lower temperature, the speed of sound will decrease. Therefore, to travel through the same distance, it will take more time. So the echo will be heard later.

Short Answer Type Questions

Question 1.
What are mechanical or elastic waves? Give examples.
Answer:
The waves which require a material medium for their propagation are called f mechanical waves. They are also called elastic waves because their propagation depends on the elastic properties of the medium.

Examples of mechanical waves:
(a) Sound waves in air.
(b) Waves over water surface.
(c) Waves produced during earthquake (seismic waves).

JAC Class 9 Science Important Questions Chapter 12 Sound

Question 2.
What are electromagnetic waves? Cite examples.
Answer:
The waves which do not require a material medium for their propagation are called electromagnetic waves. Such waves travel through vacuum with a speed of 3 × 108 m/s.
Examples of electromagnetic waves:
(a) Light waves
(b) X – rays
(c) Radio waves
(d) Microwaves

Question 3.
Define ‘crests’ and ‘troughs’ of a wave.
Answer:
In transverse waves, the particles of the medium which have maximum displacement in the positive Y – direction are called ‘crests’ while those which have maximum displacement in the negative Y – direction are called ‘troughs’.

Question 4.
Define the terms ‘compressions’ and ‘rarefactions’.
Answer:
When longitudinal waves pass through a medium, these cause pressure variations in different parts of the medium. The regions of increased pressure are called ‘compressions’ and the regions of decreased pressure are called ‘rarefactions’.

Question 5.
Differentiate between sound and light waves.

Sound wave Light wave
(a) Travels in the form of longitudinal wave. (a) Travels in the form of transverse wave.
(b) Requires a medium for its propagation. (b) Does not require a medium for its propa – gation.
(c) Travels through air with a speed of 332 m/s at 0°C. (c) Travels through air with a speed of nearly 3 × 108 m/s.

Question 6.
Why are the longitudinal waves also called pressure waves?
Answer:
Longitudinal waves travel in a medium as a series of alternate compressions and rarefactions, i.e., as they travel, there is a variation in pressure across the medium. Therefore, they are called pressure waves.

Question 7.
Derive a relation between wavelength, frequency and velocity of a wave.
Answer:
Frequency, wavelength and wave velocity are related as follows: Wavelength is the distance travelled by the wave during the time a particle of the medium takes to complete one vibration. Therefore, if λ be the wavelength and T be the time – period, the wave travels a distance λ in time T.
Hence, Wave velocity = \(\frac{Distance}{Time}\)
⇒ v = \(\frac{\lambda}{\mathrm{T}}\)
⇒ v = λ v
∵ {\(\frac{1}{T}\) = frequency (v)}
∴ Wave velocity = Frequency × Wavelength
The wave velocity in a medium remains constant under the same physical conditions.

Question 8.
On what factor does the frequency of a wave depend?
Answer:
Frequency of a wave is given by,
v = \(\frac{\mathrm{v}}{\lambda}\)
Where,
v is the speed with which the wave propagates, and λ is the wavelength of the wave. Different sources produce oscillations of different frequencies depending on the wavelength of the sources. Frequency changes such that the speed remains constant.

Question 9.
A boat at anchor is rocked by waves whose consecutive crests are 100 m apart. The wave velocity of the mocking crests is 20 m/s. What is the frequency of rocking of the boat?
Answer:
Wavelength, λ = Distance between two successive crests = 100 m
Velocity, v = 20 m/s
Frequency, v = \(\frac{\mathrm{v}}{\lambda}\) = \(\frac{20}{100}\) = 0.20 Hz.

Question 10.
Why do the animals behave in apeculiar manner before an earthquake?
Answer:
When the earthquake strikes, it produces low frequency infrasounds before the main shock waves. These infrasonic waves are not audible to the human ears. But animals are able to detect these waves and hence some animals get disturbed before earthquakes and start behaving in a different manner.

JAC Class 9 Science Important Questions Chapter 12 Sound

Question 11.
Differentiate between longitudinal wave and transverse wave.
Answer:

Longitudinal wave Transverse wave
(a) It needs a medium for propagation. (a) It may or may not need a medium for propagation.
(b) Particles of the medium move in a direction parallel to the direction of propagation of the disturbance. (b) Particles of the medium move in a direction perpendicular to the direction of propagation of the disturbance.
Example: Sound wave. Examples: Light wave and seismic wave.

Question 12.
What are multiple echoes? Give examples.
Answer:
The successive reflection of a sound wave from a number of obstacles results in hearing the echo of the sound transmitted one after the other. When a sound is repeatedly reflected between two parallel distant buildings or cliffs, multiple echoes are produced. For example, rolling of thunder is due to successive reflections between clouds and land surfaces.

Question 13.
A sound wave causes the density of air at a place to oscillate 1200 times in 2 minutes. Find the time period and frequency of the wave.
Answer:
Frequency = \(\frac{1200}{2 \times 60}\) = 10 Hz.
Time period = ?
Frequency = \(\frac{1}{\mathrm{~T}}\)
T = \(\frac{1}{Frequency}\) = \(\frac{1}{10}\) = 0. 1s.

Analysing & Evaluating Questions

Question 14.
The speed of certain waves depends on the source and the medium through which they travel.
1. What kind of waves are these?
2. Give one example of the answer to (a).
Answer:

  1. These waves are mechanical waves.
  2. Sound waves, water waves, string waves are mechanical waves.

Question 15.
The sound of an explosion on the surface of a lake is heard by a boatman 100 m away and by a diver 100 m below the point of explosion.
1. Who will hear the sound of explosion first?
2. If sound takes time t seconds to reach the boatman, how much time (approximately) will it take to reach the diver?
Answer:
1. The diver who is 100 m below the point of explosion will hear the sound of explosion first because sound travels much faster in water than in air.

2. Time taken by sound to reach the diver
= \(\frac{ Speed of sound in air × t}{Speed of sound in Water }\)
= \(\frac{344 \mathrm{~m} \mathrm{~s}^{-1}}{1533 \mathrm{~m} \mathrm{~s}^{-1}} \times \mathrm{ts}\)
= 0.22 t seconds

Long Answer Type Questions

Question 1.
State the factors on which the speed of sound in a gaseous medium depends.
Answer:
The speed of sound in a gas depends on the following factors:
(a) Effect of density: At constant pressure, the speed of sound in a gas is inversely proportional to the square root of its density.
Speed of sound ∝ = \(\frac{1}{\sqrt{\text { Density of gas }}}\)

(b) Effect of humidity: Sound travels faster in moist air than in dry air.

(c) Effect of temperature: The speed of sound in a gas is directly proportional to the square root of its absolute temperature.
Speed of sound ∝= \(\sqrt{\text { Absolute temperature of gas }}\)
So, the speed of sound increases with the increase in temperature of the gas. For example, the speed of sound in air is 331 ms-1 at 0°C and 344 ms-1 at 20°C.

(d) Effect of wind: Sound is carried by air, so the speed of sound increases when the wind blows in the direction of sound and speed of sound decreases when the wind blows in the direction opposite to the direction of sound.

JAC Class 9 Science Important Questions Chapter 12 Sound

Question 2.
Explain some important applications of ultrasound in industry and medicine.
Answer:
Applications of ultrasound in industry and medicine are as follows:

  • Industrial applications:
    1. The construction of big structures like buildings, bridges, machines, scientific equipment, etc., use metallic components.
    2. The cracks or holes inside the block reduce the strength of the structure. Such defects are not visible from outside. Ultrasonic waves can be used to detect such defects.
    3. Ultrasonic waves are allowed to pass through the metal block and detectors are used to detect the transmitted waves. If there is even a small defect, the ultrasound gets reflected back and does not reach the detector. This is how the presence of a flaw or defect is detected.
  • Medical applications:
  1. Echocardiography: In this technique, ultrasonic waves are made to reflect from various parts of the heart to form the image of the heart.
  2. Ultrasonography: Ultrasonic waves can be used to develop three dimensional photographs of different parts of the human body. This technique is called ultrasonography.
    • This technique is also used to monitor the growth of a foetus inside its mother’s womb In this technique, the ultrasonic waves travel through the tissues of the body and get reflected from a region where there is a change of tissue density.
    • These waves are then converted into electrical signals that are used to generate images of the organ. These images are then displayed on a monitor or printed on a film.
  3. In surgery: Ultrasonic waves are commonly used in cataract removal. Ultrasonic waves are also used to grind small stones formed in the kidneys. These grinded grains are flushed with urine.

Question 3.
State some important characteristics of wave motion.
Answer:
Characteristics of wave motion are as follows:

  1. It is the disturbance which travels forward through the medium and not the particles of the medium. The particles of the medium merely vibrate about their mean positions.
  2. Each particle receives vibrations a little later than its preceding particle.
  3. The velocity with which wave travels is different from the velocity of the particles with which they vibrate about their mean positions.
  4. The wave velocity remains constant in a given medium while the particle velocity changes continuously during its vibration about the mean position.

Question 4.
How can a longitudinal wave be represented graphically?
Answer:
Graphical representation of a longitudinal wave:
JAC Class 9th Science Solutions Chapter 12 Sound 6
Sound propagates as density or pressure variations as shown in (a), (b) and (c).

  1. When a longitudinal wave passes through a medium, the particles of the medium come closer together and move away from one another alternately. Thus, alternate regions of increased and decreased density are created. These regions are called compressions and rarefactions respectively.
  2. The figures (a) and (b) represent the density and pressure variations, respectively, as the sound wave propagates through a medium.
    Figure (c) represents the variations of density and pressure graphically.
  3. The variation of density increases or decreases as the pressure of the medium at a given time increases or decreases with distance, above and below the average value of density and pressure.
  4. The distance between two successive compressions (C) or two successive rarefactions (R) is called wavelength. It is usually represented by λ (lambda).

Question 5.
Explain the formation of waves with the help of an example.
Answer:
A wave is a pattern of disturbance which travels through a medium due to repeated vibrations of the particles of the medium, the disturbance being handed over from one particle to the next. The motion of the disturbance is called wave motion. If we drop a pebble into a pond of still water, a circular pattern of alternate crests and troughs spreads out from the point where the pebble strikes the water surface. The kinetic energy of the pebble makes the particles which come in contact with it oscillate.

These particles, in turn, transfer energy to the particles of next layer which begin to oscillate. Energy is further transferred to the particles of the next layer which also begin to oscillate and so on. In this way, energy is carried by the waves from one part to another. Further, if we throw pieces of paper or a cork on the water surface, it will oscillate up and down about its mean position and will not move forward with the wave. This shows that it is the disturbance of the wave which travels forward and not the particles of the medium.

Question 6.
A ship sends out ultrasound that returns from the seabed and is detected after 4 s. If the speed of ultrasound through seawater is 1550 m/s, what is the distance of the seabed from the ship?
Answer:
Time between transmission and detection, t = 4s
Speed of ultrasound in sea water,
v = 1550 m/s
Distance travelled by the ultrasound
= 2 × depth of the sea = 2d
where d is the depth of the sea.
2d = Speed of sound × time = 1550 m/s × 4s = 6200m
d =\(\frac{6200}{2}\) m = 3100 m = 3.1 km.
Thus, the distance of the seabed from the ship is 3100 m or 3.1 km.

Analysing & Evaluating Questions

Question 7.
A sound were travelling in a medium is represented as shown in the figure
JAC Class 9th Science Solutions Chapter 12 Sound 7
(a) Which letter represents the amplitude of the sound wave?
(b) Which letter represents the wavelength of wave?
(c) What is the frequency of the source of sound if the vibrating source of sound makes 360 oscillations in 2 minutes?
Answer:
In the figure,
(a) The amplitude is represented by X.
(b) The wavelength is represented by Y.
(c) Frequency
= \(\frac{No. of oscillations }{ Time in sec onds}\) = \(\frac{360}{2 \mathrm{~min}}\)
= \(\frac{360}{2 \times 60 \mathrm{~s}}\) = 3s-1 = Hz

Activity-1

  • Take a tuning fork and set it vibrating by striking its prong on a rubber pad. Bring it near your ear and observe.
  • Touch one of the prongs of the vibrating tuning fork with your finger and see what happens.
  • Take a table tennis ball or a small plastic ball Now,Take a big needle and a thread, put a knot at one end of the thread, and then with the help of the needle, pass the thread through the ball. Suspend the ball from a support. Now, touch the ball gently with the prong of a vibrating tuning fork. Observe what happens.
    JAC Class 9th Science Solutions Chapter 12 Sound 8

Observations

  • A sound is heard on bringing the vibrating fork near the ear.
  • If we touch the ball with a turning fork set into vibration, the ball gets displaced from its mean position and starts oscillating.

Activity 2

  • Fill water in a beaker or a glass up to the brim. Gently touch the water surface with one of the prongs of the vibrating tuning fork, as shown in the figure.
  • Next, dip the prongs of the vibrating tuning fork in water, as shown in the figure.
  • Observe what happens in both the cases.
    JAC Class 9th Science Solutions Chapter 12 Sound 9

Observations
In both the cases, sound will be produced by the turning fork which produces ripples in water. But in case (1), ripples are produced which will move up and down and in case (2), ripples are produced which will move sideways.

Activity 3

  • Take a spring. Ask your friend to hold one of its end. You hold the other end. Now stretch the slinky as shown in the figure. Then give it a sharp push towards your friend and observe.
  • Move your hand pushing and pulling the slinky alternatively and observe again.
    JAC Class 9th Science Solutions Chapter 12 Sound 10

Observations

  • When we give a small jerk, a hump is produced and this travels forward. It represents a transverse wave.
  • When we give a sharp push, a continuous disturbance is produced. This disturbance starts moving in the forward and backward direction parallel to the direction of propagation of the disturbance. It represents a longitudinal wave.
  • If you mark a dot on the slinky, you will observe that the dot on the slinky will move back and forth parallel to the direction of the propagation of the disturbance.

Activity 4

  • Take two identical pipes, as shown in the figure. You can make pipes using a chart paper. The length of the pipes should be sufficiently long as shown.
  • Arrange them on a table near a wall.
  • Keep a clock near the open end of one of the pipes and try to hear the sound of the clock through the other pipe.
  • Adjust the position of the pipes, so that you can hear the best sound of the clock.
  • Now, measure the angles of incidence and reflection and see the relationship between the angles.
  • Lift the pipe on the right, vertically to a small height and observe what happens.
    JAC Class 9th Science Solutions Chapter 12 Sound 11

Observations

  • Reflection of sound is similar to the reflection of light, i.e., angle of incidence = angle of reflection.
  • If we lift the pipe vertically to a small height, we will not be able to hear the sound through the other end of the pipe because the incident sound wave, the reflected sound wave and the normal, all he in the same plane.

Value Based Questions

Question 1.
Sahil noticed that his pet dog was frightened and trying to hide in a safe place in his house when some crackers were burst in the neighbourhood. He realised the problem and he decided not to burst crackers during diwali or for any other celebrations.
1. What must be the range of sound of crackers?
2. Name two diseases that can be caused due to noise pollution.
3. Name the values of Sahil reflected in the above act.
Answer:

  1. The range of crackers sound must be between 20 Hz and 20 kHz.
  2. Two diseases that can occur due to noise pollution are heart attack and high blood pressure.
  3. Sahil reflects the value of respect and sensitivity for animals and caring for animals.

Question 2.
It is not advisable to construct houses near airports. Inspite of that, many new apartments are constructed near airports. Rahul files RTI and also complains to the municipal office about the same?
1. Why should we not reside near airport?
2. Name two other places where there is noise pollution.
3. What value of Rahul is reflected in this act?
Answer:

  1. The landing and taking off of the airplanes cause a lot of noise pollution which may lead to deafness, high blood pressure, and other health problems.
  2. The other two places where there is noise pollution are heavy traffic routes and railway stations or lines.
  3. Rahul shows the values of a responsible citizen and shows awareness.

JAC Class 9 Science Important Questions

JAC Class 9 Science Important Questions Chapter 1 Matter in Our Surroundings

JAC Board Class 9th Science Important Questions Chapter 1 Matter in Our Surroundings

Multiple Choice Questions

Question 1.
Evaporation of a liquid occurs at
(a) boiling point
(b) a fixed temperature
(c) temperature lower than boiling point
(d) all temperatures
Answer:
(c) temperature lower than boiling point

Question 2.
Intermolecular force of attraction is maximum in
(a) Solids
(b) Liquids
(c) Gases
(d) Plasma particles
Answer:
(a) Solids

JAC Class 9 Science Important Questions Chapter 1 Matter in Our Surroundings

Question 3.
………… will not exhibit diffusion.
(a) Hydrogen and oxygen
(b) Oxygen and water
(c) Salt and sand
(d) Sugar crystal and water
Answer:
(c) Salt and sand

Question 4.
Which of the following substances is not a solid?
(a) Air
(b) Butter
(c) Sponge
(d) Rubber band
Answer:
(a) Air

Question 5.
Which one of the following properties is not a characteristic of liquids?
(a) Fluidity
(b) Definite shape
(c) Definite volume
(d) Compressibility
Answer:
(b) Definite shape

Question 6.
Fusion is the process in which
(a) liquid changes into gas
(b) solid changes into liquid
(c) solid changes into gas
(d) gas changes into solid
Answer:
(b) solid changes into liquid

Question 7.
The density of water is maximum at
(a) 0°C
(b) 100°C
(c) 4°C
(d) 273K
Answer:
(c) 4°C

Question 8.
Choose the correct statement from the following:
(a) Two gases cannot diffuse into each other.
(b) The volume of gas expands on heating.
(c) Conversion of a gas into solid is called condensation.
(d) Gases cannot diffuse in solids.
Answer:
(b) The volume of gas expands on heating.

JAC Class 9 Science Important Questions Chapter 1 Matter in Our Surroundings

Question 9.
Which among the following can exist in vapour state?
(a) Oxygen
(b) Hydrogen
(c) Carbon dioxide
(d) Water
Answer:
(d) Water

Question 10.
Cooking of rice at higher altitudes is difficult because
(a) water boils at temperature <100°C
(b) water boils at 100°C
(c) boiling point of water is constant
(d) none of the above
Answer:
(a) water boils at temperature <100°C

Question 11.
At normal pressure, the boiling point of water is
(a) 98°C
(b) 100°C
(c) 110°C
(d) 90°C
Answer:
(b) 100°C

Question 12.
Gases do not have
(a) high compressibility
(b) high fluidity
(c) high density
(d) volume
Answer:
(c) high density

Question 13.
Molecules of a liquid
(a) have very strong intermolecular forces
(b) cannot move randomly
(c) have definite shape
(d) have large intermolecular spaces
Answer:
(d) have large intermolecular spaces

Question 14.
………….. decreases the rate of evaporation.
(a) Surface area
(b) Humidity
(c) Temperature
(d) Wind
Answer:
(b) Humidity

Question 15.
…………… does not convert a liquid into vapours.
(a) Boiling
(b) Evaporation
(c) Heating
(d) Condensation
Answer:
(d) Condensation

Analysing & Evaluating Questions

Question 16.
Seema visited a Natural Gas Compressing Unit and found that the gas can be liquefied under specific conditions of temperature and pressure. While sharing her experience with friends, she got confused. Help her to identify the correct set of conditions for liquefaction of gases.
(a) Low temperature, low pressure
(b) High temperature, low pressure
(c) Low temperature, high pressure
(d) High temperature, high pressure
Answer:
(c) Low temperature, high pressure

Question 17.
Under which of the following conditions, the distance between the molecules of hydrogen gas would increase?
I. Increasing pressure on hydrogen contained in a closed container.
II. Some hydrogen gas leaking out of the container.
III. Increasing the volume of the container of hydrogen gas.
IV. Adding more hydrogen gas to the container without increasing the volume of the container.
(a) I and III
(b) I and IV
(c) II and III
(d) II and IV
Answer:
(c) II and III

Question 18.
A substance has a definite shape, fixed volume, distinct boundary and cannot be compressed. What is the physical state of this substance?
(a) Solid
(b) Liquid
(c) Gas
(d) Plasma
Answer:
(a) Solid

Assertion – Reason Questions

Directions: In the following questions, the Assertions and the Reasons have been put forward. Read the statements carefully and choose the correct alternative from the following:
(A) Both the assertion and the reason are correct and the reason is the correct explanation of the assertion.
(B) The assertion and the reason are correct but the reason is not the correct explanation of the assertion.
(C) The assertion is true but the reason is false.
(D) Both statements are false.
1. Assertion: Gases diffuse faster than liquids.
Reason: Particles of gases have higher kinetic energy than those of liquids.
Answer:
(A) Both the assertion and the reason are correct and the reason is the correct explanation of the assertion.

2. Assertion: Solids have negligible compressibility.
Reason: In solids, the intermolecular force of attraction is very strong.
Answer:
(B) The assertion and the reason are correct but the reason is not the correct explanation of the assertion.

3. Assertion: Evaporation always takes place at the surface of a liquid.
Reason: Molecules at the surface of liquids have higher temperature.
Answer:
(C) The assertion is true but the reason is false.

4. Assertion: On heating or cooling, the physical state of a substance gets changed.
Reason: State of matter can be changed only by changing its temperature.
Answer:
(C) The assertion is true but the reason is false.

5. Assertion: Solids generally lack the property of diffusion.
Reason: In solids, intermolecular space is negligible.
Answer:
(A) Both the assertion and the reason are correct and the reason is the correct explanation of the assertion.

Very Short Answer Type Questions

Question 1.
What is matter?
Answer:
Anything that has mass and occupies space is called matter. For examples, rocks, plants, paper. chalk, water, food. etc.

Question 2.
In what ways are all substances around us alike?
Answer:
All the substances are matter, i.e., they all have mass and occupy space. Therefore, they are all alike.

Question 3.
Why is the rate of diffusion faster in gases?
Answer:
Because the intermolecular force of attraction is minimum in gases.

JAC Class 9 Science Important Questions Chapter 1 Matter in Our Surroundings

Question 4.
Why are light and sound not considered as matter?
Answer:
Light and sound are not considered as matter because they have no mass and they do not occupy space.

Question 5.
Name the three states of matter.
Answer:
Solid, liquid and gas are the three states of matter.

Question 6.
Ice and water are basically the same substance. Mention two differences in their properties.
Answer:

  1. Ice: It has fixed volume and definite shape. It can be stored without a container.
  2. Water: It is a liquid and has no definite shape. It cannot be stored without a container.

Question 7.
Classify the following materials according to the state in which they exist around us. Steel, blood, air, oil, rubber, honey, carbon dioxide, kerosene, LPG, CNG, nitrogen, oxygen
Answer:

  • Solid: Steel, rubber.
  • Liquid: Blood, oil, honey, kerosene, LPG.
  • Gas: Air, carbon dioxide. CNG. nitrogen. oxygen.

Question 8.
Defineeflne boiling point.
Answer:
Boiling point ofa liquid is the temperature at which its pressure becomes equal to that of the atmospheric pressure and it starts vaporising into gaseous state.

Question 9.
Define melting point.
Answer:
The temperature at which a solid starts melting to become a liquid at atmospheric pressure is known as its melting point.

Question 10.
Latent heat of vaporisation of two liquids A and B is 100 kg and 150 kg respectively. What does It indicate?
Answer:
Latent heat of vaporisation depends on the nature of the liquid. Intermolecular

Question 11.
Which of the following shows the phenomenon of sublimation? Solid water, solid carbon dioxide, solid alcohol, solid oxygen
Answer:
Solid carbon dioxide.

JAC Class 9th Science Solutions Chapter 1 Matter in Our Surroundingss

Question 12.
How does spreading of wet clothes quicken their drying? Explain.
Answer:
Spreading of wet clothes increases surface area and so evaporation becomes faster. Thus, drying of wet clothes becomes faster by spreading them.

Question 13.
How does temperature affect the rate of evaporation?
Answer:
With increase of temperature, more number of particles get enough kinetic energy to change into the vapour state. Hence, rate of evaporation increases with increase in temperature.

Question 14.
Which will have more impact on kinetic energy: doubling mass or velocity?
Answer:
Doubling of velocity will increase kinetic energy four times. (KE = \(\frac{1}{2}\) mv2)

Question 15.
What is dry ice?
Answer:
Solid carbon dioxide obtained by cooling and applying pressure on carbon dioxide gas is called dry ice. it does not melt but directly transforms into vapour state, so it is called dry ice.

Question 16.
What is humidity?
Answer:
The air which holds water vapour is called humid air and the amount of water vapour present in the air is called humidity.

JAC Class 9th Science Solutions Chapter 1 Matter in Our Surroundingss

Question 17.
Define atmospheric pressure.
Answer:
The pressure exerted by the earth’s atmosphere at any given point is known as atmospheric pressure. The atmospheric pressure at sea level is atmosphere and is taken as the normal atmospheric pressure.

Analysing & Evaluating Questions

Question 18.
Alka was making tea in a kettle. Suddenly, she felt intense heat from the puff of steam gushing out of the spout of the kettle. She wondered whether the temperature of the steam was higher than that of the water boiling in the kettle. Comment.
Answer:
Temperature of steam is the same as that of boiling water. Intense heat of the steam is due to its high latent heat.

Question 19.
The energy changes in the following transformation are as follows:
JAC Class 9th Science Solutions Chapter 1 Matter in Our Surroundingss 2
In which of the above, the intennolecu lar forces are stronger?
Answer:
The intermolecular forces are stronger in water at 100°C.

Question 20.

You are given the following substances with their melting and boiling points.

Substance Melting Boiling point (°C) point (°C)
X 10 25
Y 50 90
Z 15 80

Identify the physical states of X,Y and Z t the temperature of 30°C.
Answer:
‘X’ is gas at the given temperatLire.
‘Y’ is solid at the given temperature.
‘Z’ is liquid at the given temperature.

Short Answer Type Questions 

Question 1.
Common salt and sugar hase similar appearance. Why are these classified as different substances?
Answer:
The substances are not classified only by their appearance. They are classified by their properties. such as density boiling point or melting point, conductivity ther mal capacit’ and other physical and chem ical properties. Common salt and sugar have diflì.rent physical and chemical prop erties and so are different substances.

Question 2.
Why do we sec water droplets collected on the outer surface of a glass container, containing Ice?
Answer:
The water vapour present in air, comes in contact with the cold outer surface of the container and gets condensed. This causes formation of water droplets.

Question 3.
liquids and gases can be compressed hut it is difficult to compress solids. Why?
Answer:
Liquids and gases have large intermolecular space. Thus on applying pressure externally on them, the molecules can corne more close, thereby minimising the space between them. But in case of solids there is no intermolecular space to do so.

Question 4.
If you open a bottle of perfume in one comer of a room, it immediately spreads throughout the room. Explain the properly insols-ed.
Answer:
The property involved is diffusion. In a gas, the particles arc free to mese an a chaotic motion at a great speed throughout its containing vessel. Thus, when you opcn a bottle of perfume in one corner, the particles of the perfume move at random motion in all directions and mix with othergas particles in the air. Thus, they reach instantaneously to our nose.

JAC Class 9 Science Important Questions Chapter 1 Matter in Our Surroundings

Question 5.
Why do people perspire a lot on a hot humid day?
Answer:
On a humid day. due to the heat, our body starts sweating for thecooling mechanism by evaporation. However, the humid air cannot hold any more water on a humid das and therefore the rate of evaporation decreases. Hence. sweat or perspiration is seen.

Question 6.
Hoss does the rate of diffusion change with (a) density of liquid and (b) temperature? Gise examples.
Answer:
(a) Rate of diffusion decreases with density of s liquid. Honey is denser than ink. If you add a drop of ink and honey ‘n two separate jars filled with water, it will be ohscned that honey takes longer time to reach the bottom of the jar than by the ink.

(b) Diffision increases with rise of iempersture. For example, liquids mix faster at higher temperaiures.

Question 7.
How do you differentiate between solids, liquids and gases on the basis of their inciting poInts 2nd boiling points?
Answer:

  • Solids: They hase melting and boiling points abose room temperature.
  • Liquids: They hase melting pointa below room temperature and boiling point abose room temperature.
  • Gases: They have both melting and boiling points below room temperature.

Question 8.
Which property of the gas is utilised when natural gas is supplied for vehicles?
Answer: A gas is highly compressible and a large quantity of it can be compressed to a small volume. Therefore, natural gas is compressed and is supplied for use by vehicles in the form ofCNG (Compressed Natural Gas).

Question 9.
On a hot das, why do people sprinkle waler on (be roof or open ground?
Answer:
On a bot das, the surface of roof or ground absorbs large amount of heat and remains bot. On sprinkling water on these surfaces, the water absorbs large amount of heai from 11w surface due to its high laient heat of sapsietsation and ewaporates. thereby allowing the hot surface to cool.

Question 10.
Esplain how dIffusion nf gases In water is essenilal?
Answer:
The gases from the atmosphere diffuse and dissolve in water. Difluasion of gases like oxygen and carbon dioxide ¡n water is essential for tIse survival ni aquatic animals and plants! Aninsals breathe – in this oxygen dissolved in watet foe their survival and planis can use carbon dioxide
dissolved in water foe photosynthesis.

Question 11.
Why are liqnids and gases called fluids?
Answer:
Liquids and gases can flow. Liquids can flow from higher pressure to lower pressure. The gases flow in all available directions. Due to this property of flowing, both of them are called fluids.

Question 12.
On a hot day, why do we feel pleasant sitting under a tree?
Answer:
Trees have a lot of leaves which constantly show transpiration. Transpiration is the loss of water through tiny pores of leaves called stomata. When this water comes on the surface of leaf the water evaporates, thereby causing a cooling effect. Therefore, we feel pleasant sitting under the tree on a hot sunny day.

JAC Class 9th Science Solutions Chapter 1 Matter in Our Surroundingss

Question 13.
How is the high compressibilit property of gas useful to us?
Answer:
The gases have high compressibility. This property is used in the following
situations:

  1. LPG is a fuel which is made up of petroleum gas. On compressing this petroleum gas. it forms liquid.
  2. Oxygen cylinders in the hospitals have compressed gas filled in it.
  3. CNG is a natural gas, which is compressed and used as a fuel in vehicles.

Question 14.
What ¡s pressure? What is its unit? On what factor does the pressure of a gas depend?
Answer:
The pressure exerted by a gas is the force exerted by gas particles per unit area on the walls of the container. It is expressed in pascal (Pa). I atmosphere 101325 x 10 Pa. The pressure depends on the average kinetic energy of the particles which depends on temperature of the gas.

Question 15.
How would you show that the three states of matter are interchangeable?
Answer:
On heating a solid substance and then cooling the vapour formed, we can show that the three states of matter arc interchangeable. Take ice cubes in a beaker and heat. Ice changes into water. On further heating, water changes into steam. On cooling, water vapour again changes into water and on further cooling water changes to ice.
JAC Class 9th Science Solutions Chapter 1 Matter in Our Surroundingss 3

Question 16.
Chee freezes at room temperature but mustard oil does not freeze even in winters. Which of these has a higher melting point and lower intermolecular forces?
Answer:
Ghee freezes at room temperature but mustard oil does not, it shows that intermolecular forces in ghee are stronger than those in mustard oil. The higher the intermolecular forces, the higher is the melting point. Therefore, ghce has a higher melting point than that of mustard oil.

Question 17.
Define evaporation.
Answer:
The phenomenon of change of a liquid into vapours at any temperature below its boiling point is called evaporation. Water, if left in an open vessel at room temperature, disappears after some time due to evaporation.

Question 18.
Is it true to say that fluorescent tubes contain only plasma?
Answer:
It is not correct to say that fluorescent tube contains only plasma. Inside a fluorescent tube there is helium gas or some other gas. The gas gets ionised or charged when electrical energy flows through it.

Analysing & Evaluating Questions

Question 19.
A sample of water under study was found to boil at 102°C at normal pressure. It the water pure? Will this water freeze at 0°C? Comment.
Answer:
(a) The given sample of water is not pure.
(b) The given sample of water will not freeze 0°C. The impurities raise the boiling point and lower the freezing point of water. Therefore, the given sample of water will freeze below 0°C.

Question 20.
A strong smelling gas ¡s stored in cylinders as liquid, but it comes out of the cylinder as gas.
(a) Name the gas.
(b) Vhat causes this change in state?
(c) Name the process of this conversion.
Answer:
(a) LPG (Liquefied Peroleum Gas).
(b) LPG gets converted into gas due to lowering of pressure.
(c) Vaporisation.

Long Answer Type Questions

Question 1.
Discuss the factors which affect evaporation.
Answer:
1. Surface area: Evaporation is a surface phenomenon. Thus, escaping of particles from liquid state to vapour state depends on surface area. Therefore, the rate of evaporation increases with surface area.

2. Temperature: If the temperature is increased, the rate of evaporation also increases. Due to increase in temperature, the particles gain more kinetic energy and change their phase from liquid to gaseous. Water will evaporate faster in sun than in shade.

3. Humidity: Humidity is the amount of water vapour present in the air. At a given temperature, air cannot hold more than a fixed amount of water vapour. Therefore, the rate of evaporation decreases with increase in the humidity of air.

4. Wind speed: With the increase in wind speed, the rate of evaporation increases. The particles of water vapour move away with the wind, decreasing the amount of water vapour in the surroundings.

JAC Class 9 Science Important Questions Chapter 1 Matter in Our Surroundings

Question 2.
How are particles of matter affected with increasing or decreasing pressure on the matter at a given temperature?
Answer:
On increasing pressure, particles of a matter come closer and move apart when pressure is reduced at a given temperature. Thus, if pressure is increasingly applied on a gas, particles of the gas come closer and closer and eventually the gas may change into liquid and then into solid form.
JAC Class 9th Science Solutions Chapter 1 Matter in Our Surroundingss 4

Question 3.
What is sublimation? With the help of an activity describe the sublimation of a solid substance. Name two substances used in our daily life that sublime on heating.
Answer:
We know that matter changes its state on heating from solid to liquid and from liquid to gas. However, there are some substances that change directly from solid state to gaseous state. This change of state from solid to gas without changing into liquid state is called sublimation. For example, camphor and ammonium chloride on heating change directly into vapour.

Activity

Take some ammonium chloride. Powder it and put in a china dish. Cover the china dish with an inverted funnel. Take some cotton and plug the stem of the funnel. Now, heat the china dish.
You will observe fine crystal particles depositing on the innerwalls ofthe funnel. Thus on heating, ammonium chloride is directly converted into ammonium chloride vapours which condense on the inner walls of the china dish.
JAC Class 9th Science Solutions Chapter 1 Matter in Our Surroundingss 5

Question 4.
Explain the diffusion of copper sulphate solution into water.
Answer:
The copper sulphate crystals dissolve slowly and form a layer of copper sulphate solution in the beaker. This blue copper sulphate solution diffuses into clear water and clear water diffuses down towards blue solution. This diffusion goes on until the whole water turns blue. So the spreading of blue colour is due to the diffusion of the blue copper sulphate solution and water into each other.

JAC Class 9 Science Important Questions

JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3

Jharkhand Board JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 Textbook Exercise Questions and Answers.

JAC Board Class 10 Maths Solutions Chapter 12 Areas Related to Circles Exercise 12.3

Unless stated otherwise, use π = \(\frac{22}{7}\)

Question 1.
Find the area of the shaded region in the figure, if PQ = 24 cm, PR = 7 cm and O is the centre of the circle.
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 1
Solution:
Given, PQ = 24 cm, PR = 7 cm.
We know any triangle drawn from diameter RQ to the circle is 90°.
Here, ∠RPQ = 90°
In right ΔRPQ, RQ2 = PR2 + PQ2 (By Pythagoras theorem)
RQ2 = 72 + 242
RQ2 = 49 + 576
RQ2 = 625
RQ = 25 cm
∴ Area of ΔRPQ = \(\frac{1}{2}\) × RP × PQ
= \(\frac{1}{2}\) × 7 × 24 = 84 cm2
∴ Area of semi-circle = \(\frac{\pi r^2}{2}=\frac{22}{7 \times 2}\left(\frac{25}{2}\right)^2\) (∵ r = \(\frac{\mathrm{PQ}}{2}=\frac{25}{2}\) cm)
= \(\frac{11 \times 625}{28}=\frac{6875}{28} \mathrm{~cm}^2\)
∴ Area of the shaded region = Area of the semi-circle – Area of right ΔRPQ
= \(\frac{6875}{28}-84\)
= \(\frac{6875-2352}{28}=\frac{4523}{28}\) cm2.

JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3

Question 2.
Find the area of the shaded region in the figure, if radii of the two concentric circles with centre O are 7 cm and 14 cm respectively and ∠AOC = 40°.
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 2
Solution:
R – radius of the bigger circle, r – radius of the smaller circle.
Area of the shaded portion = Area of sector OAC – Area of sector OBD
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 3

Question 3.
Find the area of the shaded region in the figure, if ABCD is a square of side 14 cm and APD and BPC are semicircles.
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 4
Solution:
Area of the shaded portion = Area of the square – 2 × Area of one semicircle
= (14 × 14) – 2 × \(\frac{\pi r^2}{2}\) [∵ r = 7]
= 14 × 14 – 2 × \(\frac{22}{7} \times \frac{7 \times 7}{2}\)
= 196 – 154 = 42 cm2.

Question 4.
Find the area of the shaded region in the figure, where a circular are of radius 6 cm has been drawn with vertex O of an equilateral triangle OAB of side 12 cm as centre.
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 5
Solution:
Area of the shaded portion = Area of the circle of radius 6 cm + Area of equilateral ΔABC – Area of the sector
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 6

JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3

Question 5.
From each corner of a square of side 4 cm a quadrant of a circle of radius 1 cm is cut and also a circle of diameter 2 cm is cut as shown in the figure. Find the area of the remaining portion of the square.
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 7
Solution:
Area of the shaded portion = Area of the square – Area of the 4 quadrants – Area of the circle
= (4 × 4) – 4 × area of one quadrant – area of the circle
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 8

Question 6.
In a circular table cover of radius 32 cm, a design is formed leaving an equilateral triangle ABC in the middle as shown in the figure. Find the area of the design.
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 9
Solution:
Area of the design (shaded region) = Area of the circle – Area of ΔABC
Area of equilateral triangle ABC = \(\frac{\sqrt{3} a^2}{4}\)
In ΔABC, AL ⊥ BC.
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 10
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 11

Alternative Method:
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 12
Area of shaded region
= 3[Area of segments]
= 3[Area of sector – Area of ΔOBC]
= 3[\(\pi r^2 \frac{\theta}{360^{\circ}}-\frac{1}{2}\) × BC × OL]

Question 7.
In the figure, ABCD is a square of side 14 cm. With centres A, B, C and D, four circles are drawn such that each circle touches externally two of the remaining three circles. Find the area of the shaded region.
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 13
Solution:
Area of the shaded region = Area of the square – Area of the 4 quadrants
= Area of the square – 4 × area of one quadrant
= (14)2 – 4 × \(\frac{1}{4}\)πr2
= (14)2 – 4 × \(\frac{1}{4} \times \frac{22}{7}\) × 7 × 7
= 196 – 154
= 42 cm2.

JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3

Question 8.
The figure depicts a racing track whose left and right ends are semicircular.
The distance between the two inner parallel line segments is 60 m and they are each 106 m. long. If the track is 10 m wide, find:
(i) the distance around the track along its inner edge.
(ii) the area of the track.
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 14
Solution:
i) Distance around the inner track
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 15
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 16

ii) Area of the track:
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 17
Area of the track = l × b + l × b + 2\(\left[\frac{\pi \mathrm{R}^2}{2}-\frac{\pi \mathrm{r}^2}{2}\right]\) r = 30 mts, R = (30 + 10) = 40 mts.
= 106 × 10 + 106 × 10 + 2 × \(\frac{\pi}{2}\)(R2 – r2)
= 1060 + 1060 + \(\frac{22}{7}\)[402 – 302]
= 2120 + \(\frac{22}{7}\)[1600 – 900]
= 2120 + \(\frac{22}{7}\)[700]
= 2120 + 2200
= 4320 m2.

Question 9.
In the figure, AB and CD are two diameters of a circle (with centre O) perpendicular to each other and OD is the diameter of the smaller circle. If OA = 7 cm, find the area of the shaded region.
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 18
Solution:
Given,
OA = 7 cm
∴ OD = 7 cm
Now, area of smaller circle whose diameter (OD) = 7 cm is
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 19
Now,
Area of ΔABC = \(\frac{1}{2}\) × AB × OC
= \(\frac{1}{2}\) × 2 × OA × OC
= \(\frac{1}{2}\) × 14 × 7 (∵ OA = OC)
= 49 cm2.
Area of semi-circle ABCA = \(\frac{\pi r^2}{2}=\frac{22}{7 \times 2}(7)^2\)
= 77 cm2
∴ Area of segments BC and AC = Area of semi-circle – Area of AABC
= 77 – 49 = 28 cm2
∴ Area of total shaded region = Area of small circle + Area of segments BC and AC
= \(\frac{77}{2}\) + 28
= 38.5 + 28
= 66.5 cm2.

JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3

Question 10.
The area of an equilateral triangle ABC is 17320.5 cm2. With each vertex of the triangle as centre, a circle is drawn with radius equal to half the length of the side of the triangle. Find the area of the shaded region. (Use π = 3.14 and \(\sqrt{3}\) = 1.73205).
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 20
Solution:
Area of the shaded portion = Area of equilateral ΔABC – Area of sector Axy – Area of sector Bxz – Area of sector Cyz.
π = 3.14, θ = 60°, r = ?, r = \(\frac{a}{2}\)
Area of the shaded portion = Area of the equilateral Δ – 3 × Area of one sector
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 21
Area of the shaded region = Area of ΔABC – \(\frac{3 \times \pi r^2 \theta}{360}\)
= 17320.5 – \(\frac{3 \times 3.14 \times 100 \times 100 \times 60}{360}\)
= 17320.5 – 1.57 × 10000
= 17320.5 – 15700.0
= 1620.5 sq.cm.

Question 11.
On a square handkerchief, nine circular designs each of radius 7 cm are made. Find the area of the remaining portion of the handkerchief.
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 22
Solution:
Number of circular designs = 9
Radius of the circular design = 7 cm
There are three circles in one side of the square handkerchief.
∴ Side of the square = 3 × diameter of circle = 3 × 14 = 42 cm
Area of the square = 42 × 42 cm2 = 1764 cm2
Area of the circle = πr2 = \(\frac{22}{7}\) × 7 × 7 = 154 cm2
Total area of the design = 9 × 154 = 1386 cm2
Area of the remaining portion of the handkerchief = Area of the square – Total area of the design
= 1764 – 1386
= 378 cm2.

Question 12.
In the figure, OACB is a quadrant of a circle with centre O and radius 3.5 cm. If OD = 2 cm find the area of the (i) quadrant OACB, (ii) shaded region.
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 23
Solution:
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 24

Question 13.
In the figure, a square OABC is inscribed in a quadrant OPBQ. If OA = 20 cm, find the area of the shaded region. (Use π = 3.14)
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 25
Solution:
Radius of the quadrant = Diagonal of the square (OB)
OB2 = OA2 + AB2
= 202 + 202
= 400 + 400
= 800
OB2 = 400 × 2
OB = \(\sqrt{400 \times 2}\) = 20\(\sqrt{2}\)
Area of the shaded region = Area of the quadrant OPBQ – Area of the square OABC
= \(\frac{1}{4}\) πr2 – (OA)2
= \(\frac{1}{4}\) × 3.14 × 20\(\sqrt{2}\) × 20\(\sqrt{2}\) – (20)2
= \(\frac{1}{4}\) × 3.14 × 400 × \(\sqrt{4}\) – 400
= \(\frac{1}{4}\) × 3.14 × 400 × 2 – 400
= 100 × 2 × 3.14 – 400
= 100 × 2(3.14 – 2)
= 200 × 1.14
= 228 sq.cm.

JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3

Question 14.
AB and CD are respectively arcs of two concentric circles of radii 21 cm and 7 cm and centre O. If ∠AOB = 30°, find the area of the shaded region.
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 26
Solution:
R = 21, r = 7, θ = 30°, π = \(\frac{22}{7}\)
Area of the shaded region = Area of sector OAB – Area of sector OCD
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 27

Question 15.
In the figure, ABC is a quadrant of a circle of radius 14 cm and a semicircle is drawn with BC as diameter. Find the area of the shaded region.
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 28
Solution:
BC2 = 142 + 142
BC2 = 196 + 196 = 392
BC = \(\sqrt{392}\) = \(\sqrt{196 \times 2}\) = 14\(\sqrt{2}\) = d
r = \(\frac{14 \sqrt{2}}{2}=7 \sqrt{2}\)
Radius of the sector = 14.
Area of the shaded region Area of the semicircle BEC – Area of the segment BDCB
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 29

JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3

Question 16.
Calculate the area of the designed region in the figure common between the two quadrants of circles of radius 8 cm each.
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 30
Solution:
Area of the design = Area of sector DXB + Area of ΔDCB
Area of the segment DXB = Area of the sector DXBC – Area of ΔDCB
JAC Class 10 Maths Solutions Chapter 12 Areas Related to Circles Ex 12.3 31

JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.4

Jharkhand Board JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.4 Textbook Exercise Questions and Answers.

JAC Board Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Exercise 13.4

Use π = \(\frac{22}{7}\), unless stated otherwise.

Question 1.
A drinking glass is in the shape of a frustum of a cone of height 14 cm. The diameters of its two circular ends are 4 cm and 2 cm. Find the capacity of the glass.
Solution:
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.4 1

Question 2.
The slant height of a frustum of a cone is 4 cm and the perimeters (circumference) of its circular ends are 18 cm and 6 cm. Find the curved surface area of the frustum.
Solution:
C.S.A. of the frustum = πl(r1 + r2)
2πr1 = 18
r1 = \(\frac{18}{2 \pi}=\frac{9}{\pi}\)
2πr2 = 6
r2 = \(\frac{6}{2 \pi}=\frac{3}{\pi}\)
C.S.A. of the frustum = xl(r1 + r2)
= π × \(4\left[\frac{9}{\pi}+\frac{3}{\pi}\right]\)
= π × 4 × \(\frac{12}{\pi}\)
= 48 cm2.3

JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.4

Question 3.
A fez, the cap used by the Turks, is shaped like the frustum of a cone. If its radius on the open side is 10 cm, radius at the upper base is 4 cm and its slant height is 15 cm, find the area of material used for making it.
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.4 2
Solution:
r1 = 4, r2 = 10, l = 15
Area of the material used = C.S.A. of the frustum + Area of the circular top
= πl(r1 + r2) + πr12
= \(\frac{22}{7}\) × 15 (4 + 10) + π × 42
= \(\frac{22}{7}\) × 15 × 14 + \(\frac{22}{7}\) × 16
= \(\frac{22}{7}\)(210 + 16)
= \(\frac{22}{7}\) × 226
= \(\frac{4972}{7}\)
= 710\(\frac{2}{7}\) cm2.

Question 4.
A container, opened from the top and made up of a metal sheet, is in the form of a frustum of a cone of height 16 cm with radii of its lower and upper ends as 8 cm and 20 cm, respectively. Find the cost of the milk which can completely fill the container, at the rate of Rs. 20 per litre. Also find the cost of metal sheet used to make the container, if it costs Rs. 8 per 100 cm2. (Take π = 3.14).
Solution:
Volume of the milk = Volume of the container = Volume of the frustum
= \(\frac{1}{3}\)πh(r12 + r22 + r1r2)   [r1 = 20, r2 = 8, h = 16]
= \(\frac{1}{3}\) × 3.14 × 16[(20)2 + (8)2 + (20 × 8)]
= \(\frac{1}{3}\) × 3.14 × 16[400 + 64 + 160]
= \(\frac{1}{3}\) × 3.14 × 16 × 624 c.c. [1 litre 1000 cc]
= \(\frac{1}{3}\) × \(\frac{3.14 \times 16 \times 624}{1000}\) litres.
Cost of the milk = \(\frac{3.14 \times 16 \times 624}{3 \times 1000}\)
= \(\frac{3.14 \times 1664}{25}\)
= 3.14 × 66.56
= 208.99 = Rs. 209.
Area of the metal sheet used = πl(r1 + r2) + πr22 [r1 = 20, r2 = 8, h = 16]
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.4 3
Area of the metal sheet used = πl(r1 + r2) + πr22
= 3.14 × 20(20 + 8) + 3.14 × 82
= 3.14 × 20 × 28 + 3.14 × 64
= 3.14[(20 × 28) + 64]
= 3.14(560 + 64)
= 3.14 × 624 sq. cms.
Cost of the metal sheet = Area × Rate
= 3.14 × 624 × rate
= \(\frac{3.14 \times 624 \times 8}{100}\)
= 3.14 × 624 × 0.08
= 3.14 × 49.92
= 156.7488
= Rs. 156.75.

JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.4

Question 5.
A metallic right circular cone 20 cm high and whose vertical angle is 60° is cut into two parts the middle of its height by a plane parallel to its base. If the frustum so obtained be drawn into a wire of diameter \(\frac{1}{6}\) cm, find the length of the wire.
Solution:
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.4 4

JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.3

Jharkhand Board JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.3 Textbook Exercise Questions and Answers.

JAC Board Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Exercise 13.3

Take π = \(\frac{22}{7}\), unless stated otherwise.

Question 1.
A metallic sphere of radius 4.2 cm is melted and recast into the shape of a cylinder of radius 6 cm. Find the height of the cylinder.
Solution:
R = 4.2, r = 6
Volume of the cylinder = Volume of the melted sphere
πr2h = \(\frac{4}{3}\)πR3
3πr2h = 4πR3
h = \(\frac{4 \pi \mathrm{R}^3}{3 \pi \mathrm{r}^2}\)
= \(\frac{4 \times 4.2 \times 4.2 \times 4.2}{3 \times 6 \times 6}\)
= 4 × 1.4 × 0.7 × 0.7
= 5.6 × 0.49
= 2.744 cm.
Height of the cylinder = 2.74 cm.

Question 2.
Metallic spheres of radii 6 cm, 8 cm and 10 cm, respectively, are melted to form a single solid sphere. Find the radius of the resulting sphere.
Solution:
r1 = 6 cm, r2 = 8 cm, r3 = 10 cm.
Let the radius of the resulting sphere be r cm.
Its volume = \(\frac{4}{3}\)πR3
Volume of the resulting sphere = Volume of the sphere of radius r1 + Volume of the sphere of radius r2 + Volume of the sphere of radius r3
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.3 1
Radius of the resulting sphere = 12 cm.

JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.3

Question 3.
A 20 m deep well with diameter 7 m is dug and the earth from digging is evenly spread out to form a platform 22 m by 14 m. Find the height of the platform.
Solution:
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.3 2
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.3 3

Question 4.
A well of diameter 3 m is dug 14 m deep. The earth taken out of it has been spread evenly all around it in the shape of a circular ring of width 4m to form an embankment. Find the height of the embankment.
Solution:
Volume of the earth got by digging the well = πr2h
= \(\frac{22}{7} \times \frac{3}{2} \times \frac{3}{2} \times 14\)
= 99 cm.
R = 1.5 + 4
r = 1.5
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.3 4
Area of the circular embankment around the well = πR2 – πr2
= π[(5.5)2 – (1.5)2]
= π(5.5 + 1.5) (5.5 – 1.5)
= π(7) (4).
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.3 5
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.3 6

JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.3

Question 5.
A container shaped like a right circular cylinder having diameter 12 cm and height 15 cm is full of ice cream. The ice cream is to be filled into cones of height 12 cm and diameter 6 cm, having a hemispherical shape on the top. Find the number of such cones which can be filled with ice cream.
Solution:
Volume of ice cream in the cylindrical container =
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.3 7
Alternative Method:
Number of cones will be = \(\frac{\text { Volume of cylinder }}{\text { Volume of cone }}\)
For the cylinder part,
Radius = \(\frac{12}{2}\) = 6 cm, Height = 15 cm
∴ Volume of cylinder = π × r2 × h = 540π
For the cone part,
Radius of conical part = \(\frac{6}{2}\) = 3 cm, Height = 12 cm
Radius of hemispherical part = \(\frac{6}{2}\) = 3 cm
Now,
Volume of cone = Volume of conical part + Volume of hemispherical part
\(\left(\frac{1}{3}\right)\) × π × r2 × h + \(\left(\frac{2}{3}\right)\) × π × r3
= 36π + 18π
= 54π.
∴ Number of cones = \(\frac{540 \pi}{54 \pi}\) = 10

Question 6.
How many silver coins, 1.75 cm in diameter and of thickness 2 mm, must be melted to form a cuboid of dimensions 5.5 cm × 10 cm × 3.5 cm?
Solution:
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.3 8

JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.3

Question 7.
A cylindrical bucket, 32 cm high and with radius of base 18 cm, is filled with sand. This bucket is emptied on the ground and a conical heap of sand is formed. If the height of the conical heap is 24 cm, find the radius and slant height of the heap.
Solution:
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.3 9
Volume of sand in the bucket = πr2h
= π × 18 × 18 × 32 cc.
Volume of the conical heap of sand = \(\frac{1}{3}\)πr2h
\(\frac{1}{3}\)πr2h = π × 18 × 18 × 32
πr2h = 3 × π × 18 × 18 × 32
πr2 × 24 = 3 × π × 18 × 18 × 32
r2 = \(\frac{3 \times \pi \times 18 \times 18 \times 32}{\pi \times 24}\)
r2 = 182 × 22
r = 18 × 2 = \(\frac{72}{2}\) = 36 cm.
l2 = h2 + r2
= (24)2 + (36)2
= (24 × 24) + (36 × 36)
= (2 × 12 × 12 × 2) + (3 × 12 × 12 × 3)
= 122 (4 + 9)
= 122 × 13
l = 12\(\sqrt{13}\) cm.

Question 8.
Water in a canal, 6 m wide and 1.5 m deep, is flowing with a speed of 10 km/h. How much area will it irrigate in 30 minutes, if 8 cm of standing water is needed?
Solution:
Quantity of water flowing in the canal in 1 hour = lbh
l = 10 km, b = 6 m, h = 1.5 m
10 × 1000 × 6 × 1.5 cubic metres.
The area this water can irrigate in 1 hour if 8 cm of standing water is needed
= \(\frac{10 \times 1000 \times 6 \times 1.5}{0.08}\)
8 cm = 0.08 mm
Area needed to irrigate in 30 mins. or \(\frac{1}{2}\) hr.
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.3 10

JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.3

Question 9.
A farmer connects a pipe of internal diameter 20 cm from a canal into a cylindrical tank in her field, which is 10 m in diameter and 2 m deep. If water flows through the pipe at the rate of 3 km/h, in how much time will the tank be filled?
Solution:
d = 20 cm, r = 10 cm = \(\frac{10}{100}\) = 0.1 mt, h = 3 km = 3 × 1000 m.
Volume of water that comes out of the pipe of diameter 20 cm
= πr2h
= π × 0.1 × 0.1 × 3000
= π × 30 cm.
In 1 hr. (60 mins.), volume of water that flows into the tank = π × 30
In 1 minute = \(\frac{\pi \times 30}{60}=\frac{\pi}{2}\) cm.
Volume of the cylindrical tank = πr2h = π × 5 × 5 × 2. d = 10, r = 5
\(\frac{\pi}{2}\) cubic metres of water will be filled in 1 minute
π × 5 × 5 × 2……. \(\frac{\pi \times 5 \times 5 \times 2 \times 2}{\pi}\) = 100 mins.

JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2

Jharkhand Board JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2 Textbook Exercise Questions and Answers.

JAC Board Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Exercise 13.2

Unless stated otherwise, take π = \(\frac{22}{7}\)

Question 1.
A solid is in the shape of a cone standing on a hemisphere with both their radii being equal to 1 cm and the height of the cone equal to its radius. Find the volume of the solid in terms οf π.
Solution:
The given solid is a combination of a cone and a hemisphere.
We have radius of the cone r = Radius of the hemisphere = 1 cm and height of the cone h = 1 cm.
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2 1
∴ Volume of the solid = Volume of the cone + Volume of the hemisphere
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2 2

Question 2.
Rachel, an engineering student, was asked to make a model shaped like a cylinder with two cones attached at its two ends by using a thin aluminium sheet. The diameter of the model is 3 cm and its length is 12 cm. If each cone has a height of 2 cm, find the volume of air contained in the model that Rachel made. (Assume the outer and inner dimensions of the model to be nearly the same.)
Solution:
d = 3 cm, AF = 8 cm = H, Ax = Fy = 2 cm = h, r = \(\frac{3}{2}\)
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2 3
Volume of the model = Volume of the cone ABC + Volume of the cylinder BCED + Volume of the cone DEF
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2 4

JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2

Question 3.
A gulab jamun contains sugar syrup up to about 30% of its volume. Find approximately how much syrup would be found in 45 gulab jamuns, each shaped like a cylinder with two hemispherical ends with length 5 cm and diameter 2.8 cm.
Solution:
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2 5
Volume of 1 jamun = Volume of the cylinder + 2 × Volume of the hemisphere
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2 6

Question 4.
A pen stand made of wood is in the shape of a cuboid with four conical depressions to hold pens. The dimensions of the cuboid are 15 cm by 10 cm by 3.5 cm. The radius of each of the depressions is 0.5 cm and the depth is 1.4 cm. Find the volume of wood in the entire stand.
Solution:
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2 7
Volume of wood in the stand = Volume of the cuboid – Volume of wood lost in making four conical depressions
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2 8

Question 5.
A vessel is in the form of an inverted cone. Its height is 8 cm and the radius of its top, which is open, is 5 cm. It is filled with water up to the brim. When lead shots, each of which is a sphere of radius 0.5 cm are dropped into the vessel, one-fourth of the water flows out. Find the number of lead shots dropped in the vessel.
Solution:
Volume of water in the cone = \(\frac{\pi r^2 h}{3}\)
= \(\frac{1}{3} \times \frac{22}{7}\) × 5 × 5 × 8 cc.
= \(\frac{22 \times 25 \times 8}{21}\) c.c.
When some lead shots are dropped into the vessel, volume of the water that flows out
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2 9
= \(\frac{1}{4} \times \frac{22 \times 25 \times 8}{21}\)
= \(\frac{22 \times 25 \times 2}{21}\) cc
This is equal to the volume of the lead shots dropped.
Volume of a lead shot = \(\frac{4}{3}\)πr3
Let the no. of lead shots dropped be x.
The volume of x lead shots = Volume of water overflown
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2 10
Number of lead shots dropped = 100.

JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2

Question 6.
A solid iron pole consists of a cylinder of height 220 cm and base diameter 24 cm, which is surrounded by another cylinder of height 60 cm and radius 8 cm. Find the mass of the pole, given that 1 cm3 of iron has approximately 8 g mass. (Use π = 3.14).
Solution:
R = 12, r = 4.
Common factor of 144 and 64 is 16 (HCF)
HCF of 220 and 60 is 20.
1 kg = 1000 gms.
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2 11
Volume of the given solid = Volume of the bigger cylinder + Volume of the surmounted cylinder
= πR2H + πr2h
= 3.14 × 122 × 220 + 3.14 × 82 × 60
= 3.14 × 144 × 220 + 3.14 × 64 × 60
= 3.14 × 16 × 20(9 × 11 + 4 × 3)
= 3.14 × 320(99 + 12)
= 3.14 × 320 × 111 c.c.
Mass of the solid = Volume × density
= 3.14 × 320 × 111 × 8 gm
= \(\frac{3.14 \times 320 \times 111 \times 8}{1000}\)kg.
= \(\frac{3.14 \times 32 \times 888}{100}\)
= 3.14 × 32 × 8.88
= 892.26 kg.

Question 7.
A solid consisting of a right circular cone of height 120 cm and radius 60 cm standing on a hemisphere of radius 60 cm is placed upright in a right circular cylinder full of water such that it touches the bottom. Find the volume of water left in the cylinder, if the radius of the cylinder is 60 cm and its height is 180 cm.
Solution:
h = 180 (cylinder), H = 120 (Cone).
Volume of the solid given = Volume of the cone + Volume of the hemisphere
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2 12
Volume of water left in the cylinder = Volume of water in the cylinder – Volume of the solid immersed
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2 13
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2 14

JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2

Question 8.
A spherical glass vessel has a cylindrical neck 8 cm long, 2 cm in diameter; the diameter of the spherical part is 8.5 cm. By measuring the amount of water it holds, a child finds its volume to be 345 cm3. Check whether she is correct, taking the above as the inside measurements, and π = 3.14.
Solution:
r = \(\frac{8.5}{2}\), R = \(\frac{2}{2}\) = 1
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2 15
Volume of water in the vessel = Volume of water in the spherical part + Volume of water in the cylindrical neck.
JAC Class 10 Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.2 16
= 3.14 × 110.354 = 346.51 cm3.
The child’s answer is wrong.