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Question
A body of mass 100 kg is lifted up by 10 m. Find :
(i) the amount of work done
(ii) potential energy of the body at that height (value of g = 10 m/s2)
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Solution
(i) Mass of the body, (m) = 100 kg
Height above the ground, (h) = 10 m
Acceleration due to gravity, (g) = 10 m/s2
We can calculate the work done against gravity as,
Work done in lifting a body = (Weight of body) × (Vertical distance)
So, W = (m) × (g) × (h)
So work done,
W = (100) × (10) × (10) J
= 10 KJ
(ii) Potential energy of a body kept at the same height is equal to the amount of work done against gravity in moving the body to that position. Therefore, the potential energy of the body at that height is 10 KJ .
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