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Question
A boy weighing 25 kgf climbs up from the first floor at height 3 m above the ground to the third floor at height 9m above the ground. What will be the increase in his gravitational potential energy? (Take g = 10 N kg -1)
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Solution
Force of gravity on boy = mg = 25 × 10 = 250N
Increase in gravitational potential energy = Mg (h2-h1)
= 250 × (9−3)
=250 × 6 = 1500 J
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