WORK AND ENERGY Q/A .

1. Explain

Energy, work, potential energy, kinetic energy,

a. Energy - The capacity to do work is called as energy.

b. Work - When force is applied and the object is set in motion or the direction of moving object changed, work is said to be done.

c. Potential energy - potential to do work because of stored up energy is called as potential energy.

d. Kinetic energy - The energy that a moving object gets because of its motion is called kinetic energy. Every moving object possesses kinetic energy.

2. Match the column

Group – A                                           Group – B

A. Machine.                                        (1)  chemical energy

B. Winding up clockwork.             (2) kinetic energy

C. Digestion, excretion.                 (3) mechanical energy

D. Rolling object.                              (4) chemical energy

E. Wood                                               (5) potential energy

3. Answer in brief

A. When can we say that something has been set in motion?

And: When force is applied, the object is set in motion or the direction of moving object changed. The object displaced from it's original place is said to be in motion.

B. What effects can be seen where force is applied to an object?

When force is applied to an object

1) It is set in motion

2) direction of motion of the object changes.

3) Change in speed of the moving object.

4) Change in the shape of the object.

C. What factors must be considered in order to measure work?

Ans: 1)For measurement of work two factors must be considered,

a) the force applied

b) displacement of the object

2) When displacement is the same, more work is done when more force is applied to it.

3) When applied force is the same, more work is done when more displacement takes place.

D. What are different forms of energy?

And: Different forms of energy are

Heat, light, sound, chemical energy, magnetic energy, electricity etc

E. Explain, heat is a form of energy.

And: Heat is used to change water into steam.

When water is heated up under pressure, a jet of steam comes out.

The energy in the jet of steam is used in steam engines or turbines

Here work is done by using heat to change water into steam hence, heat is a form of energy.

4. Fill in the blanks with the word from the bracket.

(energy, work, physical, more, chemical)

A. No ...... is done unless there is displacement.

B. If the force applied is the same, then ....... work is done where displacement is more.

C. Muscles are used to do.....work.

D. Living things get.....from food.

E. Food is stored in plants in the form of........ energy .

4. Complete the table:

5. Write notes on:

A. Magnetic energy

Ans: (1) Magnetic force can be used to do work. (2) Big machines have been designed to make use of the forces of attraction and repulsion of magnetic energy to perform work. (3) Magnetic lifts are used to lift heavy loads. (4) Magnetic belt is used to separate iron from other scrap. (5) The Maglev train moves on the principle of magnetic repulsion.

B. Electrical energy - generation and uses.

Ans: Generation - Electricity is generated through hydroelectric power plants. Water falling from great heights is used to generate electricity at such power stations. Electricity is also generated from solar power and Atomic energy. Wind energy and tidal energy are also utilized for production of electricity.

Uses - Electricity is a form of energy. It is used in several gadgets at home such as fan, fridge, washing machine, water heater etc.

Electricity is also used to run factories and trains.

C. Gobar gas - production and uses

Ans: Production - Gobar gas or bio gas is a non convention source of energy. Cow-dung, plant refuse, etc are used as energy source in gobar gas. In a gobar gas plant, microorganisms are made to act upon animal dung. This process gives out methane or gobar gas.

Uses - Gobar gas plants have been set up in many villages. Gobar gas is used for cooking, lighting lamps and also for generation of electricity. Gobar gas plants are totally eco-friendly because not only is gobar gas very convenient to use, but the process also results in the formation of an excellent manure.

7. Give examples:

(a) non conventional sources of energy

(b) Fuels

(c) Hydroelectric power plants

(d) Renewable sources of energy

(e) Never ending source of energy

(f) Machines that work on solar energy

8. Answer the following questions:

(a) Which different forms of energy are released when fireworks explode? Why?

Ans: When fireworkd explode, sound energy, light energy and heat energy are released. All these forms of energy are given out simultaneously. Substances used in making fireworks are packed in chemical energy. Therefore they explode.

(b) Why is it now necessary to use fuels with thrift?

Ans: Fuels are obtained from inside the earth. The deposits of these fuels are limited. Their consumption is increasing day by day. There is a danger that they may be used up fully one day. They are non renewable. Hence it is now necessary to use fuels with thrift.