Question

A ball is dropped vertically from rest at a height of 12 m. After striking

the ground, it bounces to a height of 9 m. What fraction of kinetic

energy does it loose on striking the ground?

Answer 1

Case I

Height of the ball = 12 m
Let mas of the ball = m,
Acceleration due to gravity = 10 m.s-2


Gravitational Potential Energy GPE 1 = m × 10 × 12

Case II
Height of the ball = 12 m
Let mas of the ball = m,
Acceleration due to gravity = 10 m.s-2

Gravitational Potential Energy GPE 2 = m × 10 ×9

GPE 1/GPE 2 = ( m × 10 × 12)/ ( m × 10 × 9)

GPE 1/GPE 2 =  4/3

GPE2/GPE1 = 3/4 

So, 

Fraction of kinetic energy does it loose on striking the ground = 1 - (3/4)

Fraction of kinetic energy does it loose on striking the ground = 1/4