Question

A Ball is dropped vertically from rest at a height of 12m. After striking the ground it bounces of 9m . What fraction of its kinetic energy does it loose on striking the ground?

Answer 1

Let mass of the ball be m.

Before Striking

Height of the ball = 12m
Potential energy = P.E = mgh

​P.E 1 = m*10*12

After Striking

Height of the ball = 9m
P.E 2 = m*10*9

Fraction

P.E 1/P.E 2 = m*10*12/m*10*9 = 3/4

Loss of K.E = 1- 3/4 = 1/4

So 1/4 of K.E is lost on striking the ground.