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Question
A man lifts a mass of 20 kg to a height of 2.5 m. Assuming that the force of gravity on 1 kg mass is 10 N, find the work done by the man.
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Solution
Mass = 20 kg h = 2.5 m
Force of gravity on a mass of 1 kg = 10 N
Force of gravity on a mass of 20kg
F = mg = 20 × 10 = 200 N
Work done in lifting the mass to height h = 20 m is
W = F × h
= 200 N × 2.5 m
= 200 × 25/10 =500 J
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