Work and Energy.

Question 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)
(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)
(c) You might have seen some beautiful fireworks during Diwali. It is an example of transformation of ....... energy into....... energy.
(light, atom, chemical, solar)
(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)
(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)
(f) The capacity that an object has for doing work is called ....... .
(energy, displacement, force)

ANSWER:

(a) A bucketful of water is to be drawn from a well. Work will be done when a force is applied to do this, because there will be a displacement of water.
(b) If a ball is dropped on the sloping roof of a house, it acquires motion and falls on the ground. That is, transformation of potential energy into kinetic energy takes place.
(c) You might have seen some beautiful fireworks during Diwali. It is an example of transformation of chemical energy into light energy.
(d) The solar cooker is an application of the heat energy of the sun, while solar cells, solar lamps are applications of the light energy of the sun.
(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 equal work will be done.
(f) The capacity that an object has for doing work is called energy.

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Question 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

ANSWER:

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

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Question 3:

Can you tell ?
(a) When can we say that displacement has taken place?
(b) What should be taken into account for measuring work?
(c) What are the various forms of energy ?
(d) Describe one natural chain of transformation of energy.
(e) Why should we save energy ?
(f) What is ‘green energy’ ?
(g) What are the non-conventional energy resources ?
(h) Which forms of energy from the sun are used in solar energy devices ?
(i) Why should we maximise the use of non-conventional energy resources ?

ANSWER:

(a) We can say that displacement has taken place when the initial and final position of an object is different i.e. there is some distance between the initial and final position of an object.

(b) While measuring work, the magnitude of force applied on an object and the displacement of an object should be taken into account.

(c) Various forms of energy are:

• Mechanical: Kinetic and potential energy are two types of mechanical energy.

• Light

• Heat

• Muscular

• Sound

• Magnetic

• Electrical

• Chemical

• Nuclear

(d) When a candle is lit, the chemical energy stored in its wax gets converted to heat and light energy.

(e) We should save energy because of the following:

• To save money: Wasting energy is same as wasting money. We all know that electricity we use at our homes isn't free but costs us a lot. So, saving energy will save money too. 
• To preserve conventional sources: Most of the energy we use in our daily life is generated using conventional energy resources, such as coal, petroleum, etc. These energy resources are non-renewable in nature. So, if we waste energy, we are indirectly wasting these resources and hence a day will come when these resources will get extinct. So to preserve these non-renewable resources, we should save energy.
• To keep environment clean: Energy saving will help us keep the environment clean. Less energy usage will result in less energy production using coal, petroleum and other conventional sources which pollutes the environment when burnt.

(f) 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) 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) Heat and light energy of Sun are used in solar energy devices.

(i) Because of 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 future. Therefore, it will be better to maximise the use of non-conventional energy resources to remove the danger of extinction of conventional energy resources.

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Question 4:

Who is the odd-one-out ?
(1) Diesel, crude oil, natural gas, wind
(2) A running car, hauling a log, a book kept on a table, picking up the school bag.
(3) Sunlight, wind, waves, 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.

ANSWER:

(1) Wind is the odd one out as it is a non-conventional energy resource. The rest are conventional energy resource.

(2) A book kept on a table is the odd one out as no work is being done in this case. In rest of the cases, work is being done.

(3) Petrol is the odd one out as it is a conventional energy resource. The rest are non-conventional energy resource.

(4) Putting off the light when going out is the odd one out as it is one of the measures of saving energy. The rest involves wastage of energy.

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Question 5:

Find out the types of energy from the following puzzle.

ANSWER: