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Question
A body of mass 10 kg falls from a height of 20 m to 8 m. Calculate:
- the loss in potential energy of the body, and
- the total energy possessed by the body at any instant? (Take g = 10 m s-2)
Solution
(i) Loss in potential energy = P.E at height 20 m – P.E. at height 8 m
= mg 20 – mg 8
= mg (20 – 8)
= mg (12) = 12 mg
= 10 × 10 × 12
= 1200 J
(ii) Say at a height 20 m above ground level
= P.E. + K.E.
= mgh + 0
= 10 × 10 × 20 + 0
= 2000 J
(∵ V = 0 when held at 10 m, Hence K.E. = 0)
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