A body is dropped from rest from a height of 10 m. If 25% of its energy is lost during collision with the ground, the greatest height it will reach after the first bounce is

2.5 m
5.0 m
7.5 m
8.2 m

Correct answer: 7.5 m

Solution

Losing 25% of the energy leaves 75% of the kinetic energy at impact, which converts to potential energy on the rebound. Maximum height = 0.75 x 10 = 7.5 m.

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