Q13 of 28 Page 159

Why does a person standing for a long time get tired when he does not appear to be doing any work.

The person standing is not doing any work externally but a lot of work is being done inside the body.

The muscle of body is stretched during standing and heart has to pump more blood to the muscle this leads to loss of energy inside body and thus he gets tired.


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11

Let us assume that you have lifted a suitcase and kept it on a table. On which of the following does the work done by you depend or not depend? Why?

a) The path taken by the suitcase.


b) The time taken by you in doing so.


c) The weight of the suitcase.


d) Your weight.

 12

When you push your bicycle up an incline, the potential energy of the bicycle and yourself increase. Where does this energy come from?

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What is kinetic energy? Derive an equation for the kinetic energy of a body of mass ‘m’ moving at a speed ‘v’.

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A free-fall object eventually stops on reaching the ground. What happens to its kinetic energy?