what work a boy of mass 50 kg will do in order to increase running speed from 9 km per hour to 18 km per hour
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Answered by
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work done is change in kinetic energy
i.e. W =
i.e. W =
siv2:
W = KE2 - KE1
so KE2 is the kinetic energy corresponding to 18 kmph
KE1 is the kinetic energy corresponding to 9 kmph
so, KE1 = 0.5 * m * v * v = 0.5*50*2.5*2.5
since 9 kmph = 2.5 m/s
so KE1 = 156.25 Joules , KE2 = 625 Joules
thus work done = KE2-KE1 = 625-156.25 = 468.75 J
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student-name Abhishek Malhotra answered this
999 helpful votes in Science, Class VIII
(1) His power will be given by the time rate of the potential energy attained by him in the whole process,
As PE = mgh, h be the net height attained by him once he puts all the steps i.e. (45 × 0.15) m
Power = mgh/time taken = (50×10×6.75)/9 = 375 Js-1
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