Chapter 11 - Work and Energy
1. Fill in each blank with the appropriate term from the brackets.
(a) A bucketful of water is to be drawn from a well. ……. will be done when a ……… is applied to do this, because there will be a ……….. of water.
(displacement, work, force)
Ans: work, force, displacement
(b) If a ball is dropped on the sloping roof of a house, it acquires …… and falls on the ground. That is, transformation of …….. energy into ………. energy takes place.
(kinetic, potential, motion)
Ans: motion, potential, kinetic
(c) You might have seen some beautiful fireworks during Diwali. It is an example of transformation of ……. energy into……. energy.
(light, atom, chemical, solar)
Ans: chemical, light
(d) The solar cooker is an application of the …… energy of the sun, while solar cells, solar lamps are applications of the …… energy of the sun.
(light, chemical, heat)
Ans: heat, light
(e) One labourer carried four pans of road metal through a distance of 100 metres. If he carries two pans of road metal through a 200 metre distance ……… work will be done.
(equal, more, less)
Ans: equal
(f) The capacity that an object has for doing work is called ……. .
(energy, displacement, force)
Ans: energy
2. Match the pairs.
| Group ‘A’ | Group ‘B’ |
|---|---|
(1) Rolling object | (a) Heat energy |
(2) Food | (b) Atomic energy |
(3) Stretched bow | (c) Kinetic energy |
(4) Sunlight | (d) Potential energy |
(5) Uranium | (e) Chemical energy |
Ans:
| Group ‘A’ | Group ‘B’ |
|---|---|
(1) Rolling object | (c) Kinetic energy |
(2) Food | (e) Chemical energy |
(3) Stretched bow | (d) Potential energy |
(4) Sunlight | (a) Heat energy |
(5) Uranium | (b) Atomic energy |
3. Can you tell?
(a) When can we say that displacement has taken place ?
Ans: When the position of the object changes, then we can say that displacement has taken place.
(b) What should be taken into account for measuring work?
Ans: While measuring work, the magnitude of force applied on an object and the displacement of an object should be taken into account.
(c) What are the various forms of energy?
Ans: Various forms of energy are:
(i) Mechanical energy
(ii) Light energy
(iii) Heat energy
(iv) Sound energy
(v) Electrical energy
(vi) Chemical energy
(d) Describe one natural chain of transformation of energy.
Ans: When a candle is lit, the chemical energy stored in its wax gets converted to heat and light energy.
(e) Why should we save energy?
Ans:
(i) Saving energy is the need of the hour.
(ii) When we produce energy, we need fuel on a large scale.
(iii) The earth’s fuel reserves are rapidly depleting.
(iv) Increased energy consumption results in increased carbon dioxide emissions.
(v) This leads to global warming and pollution.
(vi) In order to conserve our environment, we must save energy.
(f) What is ‘green energy’ ?
Ans: The forms of energy which do not produce smoke and carbon gases such as carbon dioxide or carbon monoxide are known as green energy.
(g) What are the non-conventional energy resources ?
Ans: Non-conventional energy resources are inexhaustible in nature and can be used in various forms again and again.
For example, wind energy, tidal energy, solar energy, etc. are non-conventional energy resources.
(h) Which forms of energy from the sun are used in solar energy devices ?
Ans: Heat and light energy from the sun are used in solar energy devices.
(i) Why should we maximize the use of non-conventional energy resources ?
Ans:
(i) Because of the increase in population and usage of energy resources, there is a potential danger of limited reserves of conventional energy resources, such as coal, petrol, diesel, crude oil, and natural gas, getting exhausted in the future.
(ii) Therefore, it will be better to maximise the use of non-conventional energy resources to remove the danger of the extinction of conventional energy resources.
4. Who is the odd-one-out ?
(1) Diesel, crude oil, natural gas, wind
Ans: wind.
(2) A running car, hauling a log, a book kept on a table, picking up the school bag.
Ans: a book kept on a table.
(3) Sunlight, wind, waves, petrol
Ans: petrol.
(4) Leaving the fan on in a vacant room, leaving the TV on while working, using AC during winter, putting off the light when going out.
Ans: putting off the light when going out.
5. Find out the types of energy from the following puzzle.
Ans:
