Q.1. How the bats make use of ultrasonic waves to catch their prey? Explain?
Ans. The bat produces high pitched ultrasonic waves. The waves on striking the insect return back, which is heard by the bat. On hearing the echo the bat locates the insect and catches it.
Q.2.How does the stethoscope help the doctors in listening to the sound of the patients heart beat?
Ans. In a stethoscope, the sound produced within the body of a patient is picked up by a sensitive diaphragm and then reaches the doctor's ear by multiple reflections.
Q.3. Explain how defects in a metal block can be detected using ultrasound.
Ans. To detect minor cracks or flaws in metal block, ultrasonic waves are allowed to pass through metal blocks and detectors are used to detect the transmitted waves. If there is a crack in metal block, these waves get reflected back
Q.4. How is ultrasound used for cleaning?
Ans. The object to be cleaned is put in a tank fitted with ultrasonic vibrator. The tank is filled with cleaning solution. As the ultrasonic vibrator is switched on, high frequency vibrations are set up and the dust, grease and dust particles get detached and the object gets thoroughly cleaned.
Q.5. What is echo ranging? State any one application of this technique.
Solutions for Class 9th Science: Chapter 12 Sound
CBSE NCERT IX-Physics for term-II Chapter: Sound key points
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1. A solid metallic hemisphere of radius 8 cm is melted and recasted into a right circular cone of base radius 6 cm. Determine the height of the cone.
2. A rectangular water tank of base 11 m × 6 m contains water upto a height of 5 m. If the water in the tank is transferred to a cylindrical tank of radius 3.5 m, find the height of the water level in the tank.
3. How many cubic centimetres of iron is required to construct an open box whose external dimensions are 36 cm, 25 cm and 16.5 cm provided the thickness of the iron is 1.5 cm. If one cubic cm of iron weighs 7.5 g, find the weight of the box.
4. The barrel of a fountain pen, cylindrical in shape, is 7 cm long and 5 mm in diameter. A full barrel of ink in the pen is used up on writing 3300 words on an average. How many words can be written in a bottle of ink containing one fifth of a litre?
5. Water flows at the rate of 10m/minute through a cylindrical pipe 5 mm in diameter. How long would it take to fill a conical vessel whose diameter at the base is 40 cm and depth 24 cm?
6. A heap of rice is in the form of a cone of diameter 9 m and height 3.5 m. Find thevolume of the rice. How much canvas cloth is required to just cover the heap?
7. A factory manufactures 120000 pencils daily. The pencils are cylindrical in shape each of length 25 cm and circumference of base as 1.5 cm. Determine the cost of colouring the curved surfaces of the pencils manufactured in one day at Rs 0.05 per dm2.
8. Water is flowing at the rate of 15 km/h through a pipe of diameter 14 cm into a cuboidal pond which is 50 m long and 44 m wide. In what time will the level of water in pond rise by 21 cm?
9. A solid iron cuboidal block of dimensions 4.4 m × 2.6 m × 1m is recast into a hollow cylindrical pipe of internal radius 30 cm and thickness 5 cm. Find the length of the pipe.
10. 500 persons are taking a dip into a cuboidal pond which is 80 m long and 50 m broad. What is the rise of water level in the pond, if the average displacement of the water by a person is 0.04m3?
1. 28.44 cm 2. 8.6 m 3. 3960 cm3, 29.7 kg 4. 480000 words
5. 51 minutes 12 sec 6. 4.25m3, 80.61 m2 7. Rs 2250 8. 2 hours
9. 112 m 10. 0.5 cm
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2 Marks Questions [2 x 5 = 10 ]
1. An element has electronic configuration 2, 8, 3. What is the atomic number of this element? To which (i) group and (ii) period this element belong?
2. State the positions of (i) isotopes of the same element and (ii) hydrogen in the Modern Periodic Table.
3. How does the tendency to gain electrons change as we go down the 16th group of periodic table? Why?
4. Give reasons for the following : (a) Lithium atom is smaller than sodium atom. (b) Chlorine (atomic number 17) is more electro negative than sulphur (atomic number 16)
5. (a) State the Modern Periodic Law. (b) Name the element which has twice as many electrons in its second shell as in its first shell. Write its electronic configuration also.
3 Marks Questions [ 3 x 5 = 15 ]
1. An element X belongs to group 17 and third period of the periodic table. (a) Write electronic configuration of the element. What is its valency? (b) Predict its nature, whether it is a metal or non-metal. (c) Give the formula of the compound formed when it combines with an element Y having valency three.
2. Three elements A, B and C have atomic number 7, 8 and 9 respectively. (a) What would be their positions in the Modern Periodic Table (Mention group and period both)? (b) Arrange A, B and C in the decreasing order of their size. (c) Which one of the three elements is most reactive and why?
3. (a) The elements of the second period along with their atomic number in parenthesis are given below : B (5), Be (4), O (8), N (7), Li (3), C (6), F (9) (i) Arrange them in the same order as they are in the periodic table. (ii) Which element has the (i) largest (ii) smallest atom? (b) Why does the atomic radius change as we move from left to right in a period?
4. (a) How is the valency of an element determined from its position in the periodic table? (b) Magnesium has atomic number 12. To which (i) group (ii) period of the periodic table does it belong? (c) The valency of all the elements in a group is same. Why?
5. A part of the periodic table has been shown below :
Answer the following questions on the basis of position of elements in the above table.
(a) Which element is a noble gas? Give reason.
(b) Which element is most electronegative? Give reason.
(c) Write the electronic configuration of (i) B and (ii) E.
Group → 1 2 13 14 15 16 17 18
2 A C E G
3 B D F
5 Marks Questions [ 5 x 1 = 5]
1. What are electron affinity and ionization energy? How they are vary in group and periods in modern periodic table? OR, Two elements ‘A’ and ‘B’ belong to group 1 and 2 respectively in the same period. Compare them with respect to :– (a) Number of valence electrons (b) Valency (c) Metallic character (d) Size of atom (e) Formulae of their oxides.
2 Marks Questions
1. Atomic number is 13. (i) Group – 13 (ii) 3rd Period
2. (i) All isotopes have same atomic number. So they have same place for a particular element.
(ii) Hydrogen is not given a definite position. It was placed in group I A and group VII B in the Modern Periodic Table.
3. As we go down the 16th group of periodic table, tendency to gain electrons decreases because the electronegative character (non metallic character) of elements gradually decreases.
4. As we move down in a group, an electron shell is added after every change of period. Sodium has one more shell than lithium.
Li (3) = 2, 1 Na (11) = 2, 8, 1
Due to less number of shells, lithium atom is smaller than sodium atom.
(b) The nucleus of chlorine has more tendency to attract an extra electron than the nucleus of sulphur because chlorine needs only one 1 electron to complete its shell. Hence, chlorine is more electronegative than sulphur.
5. (a) Modern Periodic Law : Properties of elements are the periodic function of their atomic numbers.
(b) Carbon (atomic number 6) has twice electrons in its second shell as compared to first shell because its electronic configuration is 2, 4.
3 Marks Questions
1. (a) Electronic configuration — 2, 8, 7. Its valency is one. (b) It is a non-metal (c) YX3
2. (a) A, B and C occupy 2nd period of periodic table and 15, 16 and 17 groups respectively.
(b) A > B > C because atomic size decreases as we move from left to right across a period.
(c) C has electronic configuration 2, 7. It needs only one electron to complete its outermost shell. So it is more reactive.
3. (a) (i) Li (3), Be (4), B (5), C (6), N (7), O (8), F (9). (ii) Li is largest and F is smallest atom.
(b) As one moves from left to right across a period, there is a consecutive addition of a proton in the nucleus that increases the positive charge, which consequently pulls the extra nuclear electrons in the outermost shell inward. Thus, atomic size decreases with the increase in the number of protons as one moves from left to right in a period.
4. (a) The valency of an element with respect to hydrogen increases from 1 to 4 and then falls to 1 as in 2nd period elements.
The valency of elements with respect to oxygen increases from 1 to 7 for 3rd period elements. (b) (i) 2nd group (ii) 3rd period
(c) In a group all elements have same number of electrons in their outermost shell. So they have same valency.
9th Chapter: Probability based on Deck (Card): Question with Solution
1. Find the probability of drawing a black card.
2. Find the probability of drawing a red card.
3. Find the probability of drawing either a red or black.
4. Find the probability of drawing an ace.
5. Find the probability of drawing either a jack or queen or king.
6.Find the probability of drawing a black king.
7. Find the probability of drawing a white queen.
8. Find the probability of drawing a club.
9. Find the probability of drawing a heart.
10. Find the probability of drawing either a spade or diamond.
11.Find the probability of drawing a club and heart.
12.Find the probability of drawing either a black card or number 10.
13.Find the probability of drawing a number more than 5.
14.Find the probability of drawing a picture card. (includes jack, queen or king)
15. Find the probability of drawing a red ace.
16. The probability of selecting neither a jack nor an ace from a well-shuffled pack of 52 playing cards is :
17. From a well shuffled pack of cards, a card is drawn at random. Find the probability of getting a black queen.
18. A card is drawn from a well-shuffled pack of 52 cards. What is the probability that it is an Ace.
19. One card is drawn from a well shuffled deck of 52 cards. Find the probability of getting a red face card.
20. The king, queen and jack of clubs are removed from a deck of 52 playing cards and the remaining cards are shuffled. A card is drawn from the remaining cards. Find the probability of getting a card of (i) heart (ii) queen (iii) clubs
Ans: (i) 3/49 (ii) 3/49 (iii) 10/49
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1. Three coins are tossed once, find the probability of getting at least one head (7/8)
2. When three coins are tossed simultaneously, find the probability of getting at least two Tails
3. Three coins are tossed simultaneously 200 times with the following frequencies of different Outcomes
Out comes 3 Heads 2 Heads 1 Head No head
Frequency 23 72 77 28
Find the probability of getting: a) 2 Heads b) at least 2 Heads
4. A dice is thrown once, find the probability of getting a prime number (1/2)
5. A Pair of dice is thrown once, find the probability of getting a doublet (1/6)
6. A dice is thrown once. Find the probability of getting:
a) An even number (1/2)
b) A prime number (1/2)
c) A number greater than 4 (1/3)
7. A fair die is tossed once. Find the probability of getting:
a) a number more than or equal to 3 ( 2/3)
b) a multiple of 3 (1/3)
8. A letter of English alphabet is choosen at random. Calculate the probability that the letter choosen is a vowel ( 5/26)
9. A bag contains 15 balls numbered 1 to 15. Find the probability of drawing a prime number, When one ball is drawn from the bag at random (2/5)
10. Marks obtained by 50 students in a class test of 100 marks are given below
Marks 0 - 25 25 - 50 50 – 75 75 - 100
No of students 4 12 18 16
Find the probability that a student obtained less than 50% marks
11. in a one day international cricket match, a batsman played 40 balls. The runs scored as Follows
Runs scored 0 1 2 3 4 6
No of balls 13 15 5 1 4 2
Find the probability that the batsmen will score:
a) 6 runs ( 1/20)
b) A four or a six run (3/20)
12. One number is chosen at random from numbers 1 to 100. Find the probability that it is Divisible by 4 or 6 (33/100)
13. In a survey of 80 people, 60 people like apple juice and remaining dislike it. Find the
Probability that people dislike apple juice (1/4)
14. 250 families with 2 children are selected randomly and following data were obtained
Number of sons in family 2 1 0
Number of families 75 125 50
Find the probability of families having
a) 2 sons b) 1 son c) no son
15. 1500 family with 2children were selected randomly and the following data was recorded
Number of girls in family 2 1 o
Number of family 475 814 211
Compute probability of a family chosen at random having
a) At most 1 girl (41/60)
b) At least 2 girls (19/60)
16. Probability of an impossible event is always………
a) 0 b) 1 c) 2 d) ½
17. A die is thrown once. The probability of getting an even prime number is
a) ½ b) 1/3 c) 1/6 d) 2/3
18. A coin is tossed once then probability of getting head is
a) 2 b) 1 c) ½ d) 3
19. There are 10 bulbs in a bag in which 4 bulbs are good and rest are fused, then the
Probability of fused bulbs is
a)3/5 b) 2/5 c) 1 d) 2/3
20. Sum of the probability of happening and not happening of an event is
a) 1 b) 2 c) 0 d) none of these
21. The probability of winning a game is 0.3. Then, the probability of losing a game is
a) 0.3 b) 0.7 c) 0.6 d) 0.1
22. The Probability of a sure event is
a) 1 b) – 1 c) 0 d) none of these
23. Out of 35 students participating in a debate 10 are girls. The probability that winner is a boy is :
a) 1/7 b) 3/7 c)4/7 d) 5/7
24. Which of the following cannot be the probability of an event
a) 1/5 b) 0.3 c) 4% d) 5/4
25. In a cricket match, a batsman hits a sixer 8 times out of32 balls played. The probability that a sixer is not hit in a ball is :
a)0.75 b) 0.25 c) – 0.25 d) 0.5
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Management of Natural Resources class 10 NCERT Questions with Solution
NCERT Solutions In-text Q & A NCERT Book - Page No 269
Q1: What changes can you make in your habits to become more environment-friendly?
Ans: The following changes can be made in our habits to become more environment-friendly:
1. By using the principle of 3R's i.e. Reduce, Reuse and Recycle.
2. Always separate the biodegradable and non-biodegradable waste;
3. Plastic, paper, or glass must be recycled or reused and not dumped with other wastes
4. Switch off the electrical appliances when not in use; Avoid wastage of energy, Water and food ;
5. Should dispose the wastes safely and not disperse in public places
6. Careful use of fuels like gas & petrol;
7. Use of alternate sources of energy;
8. By using local transport like buses or train.
9. Use of natural fertilizers like manures
2. What would be the advantages of exploiting resources with short-term aims?
Ans: Advantages of exploiting resources with short-term aims:
(i) Availability of all resources at a time;
(ii) Faster development and growth of economy;
(iii) Rapid Industrialisation;
(iv) Agricultural developments;
But we should remember that these advantages are very limited as this would lead to the depletion of natural resources for present and future generation. This may also cause havoc with the ecology of the earth.
3. How would these advantages differ from the advantages of using a long term perspective in managing our resources?
Ans: If resources are used in accordance with short term aims, present generation will be able to only utilize the resources properly for growth and development. But if we use resources with long term aims, future generation will also be able to utilize resources for fulfilling its needs. The all around growth of the world will be in a balanced manner and uniform and it would preserve our ecology. Thus it would be better to use our natural resources with a long term perspective so that it could be used by the present generation as well as conserved for future use.
4. Why do you think there should be equitable distribution of resources? What forces would be working against an equitable distribution of our resources?
Ans: There should be equitable distribution of resources so that all people, all countries will be able to fulfil its needs and could grow properly using all resources equally. Each and every one gets his share of the resource and it would fulfil the fundamental right of equality. Forces working against equitable distribution of resources are:
Natural forces: 1. Land form 2. Climate 3.Distribution of rainfall. 4. Types of soil.
Man-made forces: 1. Human greed, 2. Corruption, 3. Restrictions by higher authorities, 4. Lobby of the rich and powerful people & companies and 5. Political interferences
NCERT Solutions In-text Q & A NCERT Book - Page No 273
Q1. Why should we conserve forests and wildlife?
Ans: We should conserve forest and wildlife because:
1. To preserve the biodiversity (range of different life-forms) so as to avoid the loss of ecological stability.
2. Forests play an important role in maintaining ecological balance;
3. It may affect these habitants like tribes or rural people as it is a source of their food, shelter, & livelihood;
4. Forest provide us oxygen, medicines, etc
5. It maintains climate, hydrological cycle, quality of soil, the water sources, and the amount of rainfall;
4. Forest prevents soil erosion.
5. Plants are dependent on animals and birds for their pollination and seed dispersal.
6. Provides various forest products are used in house and as raw materials in industries. So, we can say that without forests and wildlife, we cannot imagine our life on this earth.
Q2. Suggest some approaches towards the conservation of forests.
Ans: Following measures are taken to conserve forests:
1. Conversion of forests by making more national parks, sanctuaries, biosphere and reserve forests;
2.To take help of local people who resides in and around the forests in conserving forest through awareness programmes, awards, govt. Help;
3.Not to allow the destruction of forests for making un-necessary roads, dams and hotels etc.
4.Planting more trees, and Rate of afforestation must be more than that of deforestation.
5. Govt should enact strong laws to prevent illegal forest activities and to promote better management of the forest resources.
NCERT Solutions In-text Q & A NCERT Book - Page No 276
Q1. Find out about the traditional systems of water harvesting/management in your region.
Ans: India has a long history of traditional systems of water harvesting/management. Many water harvesting structures and systems specific to the different regions and culture has been developed. They harvested the rain drop directly. From rooftops, they collected water and stored it in tanks built in their courtyards. From open community lands, they collected the rain and stored it in artificial wells. They harvested monsoon runoff by capturing water from swollen streams during the monsoon season and stored it various forms of water bodies like tanks. They harvested water from flooded rivers.
2. Compare the above system with the probable systems in hilly/ mountainous areas or plains or plateau regions.
Ans: In plains, the water harvesting structures are mostly circular shaped earthen structures. The most of the plain or desert or plateau areas are having artificial water collection areas like Baowalis, Kunds, bands, Johads, talab, etc. These are low, straight, and created by digging lands or rocks. These are used to collect waters from rain, flood, etc. In hilly regions, Kulh, Naula,Kul, Zabo, Zings are the some of the system of water harvesting/management which are followed in J&K, Himachal, Uttarakhand, and North-east areas. Most of these methods are meant to collect waters from glaciers and rain by making channels and pits.
Q3. Find out the source of water in your region/locality. Is water from this source available to all people living in that area?
Ans: The source of water in our region is River water supplied from the Yamuna canal by the local authorities. This type of Water supply is available to the limited people and not to entire population living in Gurgaon area. The Many new, un-authorised, and slum colonies use ground water through bore wells, hand pumps, etc.
NCERT Solutions Exercises Q & A NCERT Book - Page No 278
Q1. What changes would you suggest in your home in order to be environment-friendly?
Ans: Changes that can be suggested in my home to be environment-friendly are as follows:
1. Always switch off the electrical appliances & Gadgets when not in use;
2. Do not waste water and always turn off taps while brushing or bathing and get repaired the leaking taps;
3. Separate biodegradable and non-biodegradable waste into separate bins before giving to waste/garbage collectors;
4. Construct water harvesting systems and if residing in rural areas, always built composting pits;
5. Use energy efficient devices; and
6. Use of public transport as far as possible.
Q2. Can you suggest some changes in your school which would make it environment friendly?
Ans: Changes that can be implemented in my school to make it environment friendly are as follows:
1. Switching off lights and fans when not required;
2. Turn the taps off when not in use;
3. Biodegradable and non-biodegradable wastes should be separated into separate bins;
4. Proper and strong water harvesting systems;
5. Plantation of trees;
6. Organising awareness programmes for students, teachers and parents;
7. Participation in the community programmes related to environment/ecology.
Q3. We saw in this chapter that there are four main stakeholders when it comes to forests and wildlife. Which among these should have the authority to decide the management of forest produce? Why do you think so?
Ans: The forest department of the government should have the authority to decide the management of forest produces. This is because the forest department is the care taker of the forest land and is responsible for any damage to the forest. But it should take the local people & authorities along with social activists and NGOs in to its decision making body. It will help in
1. Better utilisation of resources without disturbing ecological balance;
2. Continuous monitoring to avoid excessive exploitation;
3. building the confidence of Govt among the society; and
4. also in enacting a area specific approach for the better management of forest & wildlife resources.
Q4. How can you as an individual contribute or make a difference to the management of (a) forests and wildlife, (b) water resources and (c) coal and petroleum?
Ans: (a) Forest and wildlife: (i) By making aware the general people about the benefits of forest and wildlife for society, country and ecology; 2. By telling them the better methods to promote and better manage the forest and wildlife; 3. Organise rallies and protest against the cutting of trees, poaching of wild animals, wasteful use of forest land and other illegal activities; 4. Less use of the general items which are made from the forest raw materials and 5. Continuous tree plantation through community participation. (b) Water resources: (i) Turn off taps when brushing or bathing and repair leaking taps immediately; (ii) Accepting and implementation of various rainwater harvesting methods;
(v) We should avoid the discharge of sewage and other wastes into sewage and drainage systems, rivers and other water resources.
(vi) Use of drip & sprinkle system of irrigation;
(vii) Optimum utilisation for domestic & industrial purpose.
(c) Coal and petroleum: (i) Use of public transport or practice car pooling to minimise the use fuels; (ii) Avoid or stop use of coal as a fuel; (iii)Promote the use of alternative sources of energy like solar energy instead of coal and petroleum; (iv) to develop best technology for hybrid type transports;
Q5. What can you as an individual do to reduce your consumption of the various natural resources?
Ans: I can reduce the consumption of various natural resources in the following ways: (i) stop the cutting of trees for domestic or industrial purpose;
(ii) Use recycled paper and stop using non-biodegradable substances;
(iii) Turn off taps when brushing or bathing and repair leaking taps immediately; (iv) We should practice rainwater harvesting. (v) We should practice car pooling to avoid the excessive use of petroleum. (vi) Switching off lights and fans when not required
(viii) Use of alternative sources of energy such as hydro-energy and solar energy.
Q6. List five things you have done over the last one week to (a) conserve our natural resources. (b) increase the pressure on our natural resources.
Ans: (a) To conserve our natural resources:
1. Travelled by public transports and cycle;
2. Used recycled paper;
3. Separated biodegradable and non-biodegradable waste into separate waste bags
; 4. Avoided food wastage & Planted trees
5. Reduced consumption of electricity by Switching off lights and have not used room heaters in winter;
6. Turned off taps when brushing or bathing and got repaired two leaking taps;
(b) To increase the pressure on our natural resources:
1. Sometimes in night forgot to switch off lights;
2. Used non-recycled papers for school work;
3. Used plastics and polythene bags for carrying goods;
4. Used family car to visit some places thereby wasting fuel;
5. Used room heater in night; 6. Sometimes forgot to turn-off taps while using water for bathing, etc and wasted water for gardening & car wash.
Q7. On the basis of the issues raised in this chapter, what changes would you incorporate in your life-style in a move towards a sustainable use of our resources?
Ans: I would incorporate the following below mentioned changes in my life-style in a move towards a sustainable use of our resources:
(i) Change in the personal attitudes and daily life practices;
(ii) Conservation of water by adopting the following methods:
a. Waste minimum amount of water while using and repair leaking taps
b. Practice rainwater harvesting
c. Economic use of water for domestic & industrial purpose
d. Using less water consuming technique for toilets;
e. Drip and Sprinkling irrigation methods
(iii) Conservation of energy by adopting the following methods:
a. Switching off un-necessary lights, fans, other electrical gadgets;
b. Use of public transports, cycles, and walk;
c. Use of alternate source of energy
d. Avoid using room heaters.
(iv) Stop cutting trees and practice plantation of trees.
(v) Stop using plastic and polythene bags for carrying goods.
(vi) Use principle of three Rs- reduces, recycle and re-use.
(vii) Use recycled paper.
(viii) Separation of biodegradable and non-biodegradable waste into separate bins.
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