InterviewSolution
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InterviewSolution
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Give reasons for the following:(a) No work is done ¡fa man ¡s pushing against a wall.(b) Hammer drives a nail into the wood only when it ¡s lifted up and then struck.(c) A horse and a dog are running with the same speed. Which one of them has more kinetic energy than the other.(d) A teacher moving around in the class is doing work but a child standing and reading a book is not doing any work. |
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Answer» (a) As wall does not move from its place distance moved is zero. Hence, no work is done. (b) On lifting the Hammer, its potential energy is stored in the hammer on striking the nail with a hammer this energy is used in driving the nail into the wood. (c) A horse has more mass than dog. As both are running at the same speed. M1 of horse is greater than M2 of dog ∴ K.E. of horse is more than K.E. of dog (d) A child reading a book while standing is not moving from its place i.e. displacement is zero. Hence product of force and displacement is zero W = F × S W = mg × 0 = 0 Hence, a child is not doing any work. Whereas the teacher is moving from its place is doing work. |
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