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11. Work and Energy
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Q13 of 33 Page 158

A person holds a bundle of hay over his head for 30 minutes and gets tired. Has he done some work or not? Justify your answer.

The person does not do work because no displacement takes place in the direction of applied force as the force acts in the vertically upward direction.


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What is the work done by the force of gravity on a satellite moving round the earth? Justify your answer.

12

Can there be displacement of an object in the absence of any force acting on it? Think. Discuss this question with your friends and teacher.

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An electric heater is rated 1500 W. How much energy does it use in 10 hours?

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Illustrate the law of conservation of energy by discussing the energy changes which occur when we draw a pendulum bob to one side and allow it to oscillate. Why does the bob eventually come to rest?

Questions · 33
11. Work and Energy
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