STD-VI, WORK AND ENERGY, EXERCISE QUESTION ANSWERS

 A.     FILL IN THE BLANKS.

1.      The work done depends upon the ____ applied and the _____ produced.

Ans: force, displacement

2.      _______ is the capacity to do work.

Ans: Energy

3.      _____ energy, stored in a battery, can be used to produce light in a torch.

Ans: chemical

4.      ______ is the main source of light energy.

Ans: Sun

5.      An electric bell produces sound from ______ energy.

Ans: electrical

B.      WRITE TRUE OR FALSE FOR THE FOLLOWING STATEMENTS.

 

1.      Work is done whenever a force is applied on a given object.                False

2.      A stationery ball does not possess kinetic energy.                                  True

3.      A ball raised to a height, is said to possess chemical energy.                False

4.      The motion, of the blades of a fan, is due to mechanical energy.         True

5.      Sound is a form of energy.                                                                        True

 

C.      TICK THE CORRECT OPTION.

 

1.      In which of the following situations, no ‘work’ is being done?

(a)   Shifting a box of biscuits from a lower shelf to a higher shelf in the kitchen

(b)   Throwing a ball

(c)    Pushing a baby stroller on a road

(d)   Just holding a book in your hand for two minutes

      Ans: just holding a book in your hand

 

2.      The ability, or capacity, of a body to do work is known as-

(a)   Force

(b)   Displacement

(c)    Energy

(d)   Motion        

      Ans: energy

3.      The form of energy, possessed by flowing water, is known as-

(a)   Potential energy

(b)   Kinetic energy

(c)    Chemical energy

(d)   Light energy 

       Ans: kinetic energy 

4.      The energy, associated with wind, is an example of-

(a)   Chemical energy

(b)   Kinetic energy

(c)    Potential energy

(d)   Electrical energy           

      Ans: kinetic energy

5.      When a rubber band is stretched, it can be said to have gained-

(a)   Chemical energy

(b)   Potential energy

(c)    Kinetic energy

(d)   Electrical energy

      Ans: potential energy

D.     ANSWER THE FOLLOWING QUESTIONS IN BRIEF.

 

1.      Write the meaning of the following terms.

(a)   Work         (b) energy

Ans: (a) Work- An activity, involving a force, and a net displacement, in the direction of the applied force is called as work.

               (b) Energy- It is the capacity to do work.

2.      State the conditions under which work is said to have been done.

Ans: The conditions under which work is said to have been done are,

(i) a force is applied       

(ii) displacement of the object occurs

3.      Name any three different forms of energy.

Ans: Three different forms of energy are,

(i) Chemical energy

(ii) Electrical energy

(iii) Light energy

4.      State the type of mechanical energy possessed by the following:

(a)   A bullet fired from a gun

Ans: kinetic energy

(b)   The wound up spring of a toy car

            Ans: potential energy

(c)    The water, stored at a height, in a tank

Ans: potential energy

(d)   A moving bus

Ans: Kinetic energy

5.      State two different uses of light energy.

Ans: (i) Light energy is used by plants in the process of photosynthesis.

(ii) Solar cells use light energy to produce electricity.

 

E.      ANSWER THE FOLLOWING QUESTIONS.

 

1.      Is there a difference between ‘applying a force’ and ‘doing work’? Give reason for your answer.

Ans: Yes there is a difference between ‘applying force’ and ‘doing work’.

For work to be done, there should be an applied force and displacement of the object.

Suppose a porter is holding a box on his head for 2 minutes. Here, the porter is applying force in a vertical direction. But no displacement occurs. So no work is done by the porter.

2.      Explain, by giving an example, that a moving object can do work.

Ans: Flowing water displaces the top soil from one place to another. Also, it helps in seed dispersal.

So, we can say a moving object can do work.

3.      A porter keeps standing at a place while holding a suitcase of mass 20 kg over his head for five minutes. Has he done some work? Give reason for your answer.

Ans: No, he has not done any work.

According to the conditions, if the applied force displaces an object, then work is said to be done.

But, here no displacement is produced in the suitcase. So, no work is done by the porter.

4.      Define the term ‘energy’. Describe an activity to show the inter-relationship between work and energy.

Ans: Energy is defined as the capacity to do work.

ACTIVITY:

Let’s make one simple electrical circuit using a cell, motor and metallic wires. As soon as the circuit is complete, the chemical energy of the cell is converted into electrical energy. When electricity flows through the motor, it starts rotating. Here work is being done by the chemical energy stored in the cell.

But after some time, when all the chemicals in the cell gets exhausted, the motor stops rotating.

This activity shows that energy is required to do work.

5.      Name a device which converts-

(a)   Electrical energy into light energy

Ans: LED bulb

(b)   Sound energy into electrical energy

            Ans: Microphone

(c)    Chemical energy into electrical energy

             Ans: Electric Cell