Question

A ball is moving with speed $12\text{m/s}$ towards a heavy wall which is moving towards the ball with the speed $10\text{m/s}$ as shown in figure. Assuming collision to be perfectly elastic, find the speed of ball after the collision.

• A. $2\text{m/s}$
• B. $32\text{m/s}$
• C. $14\text{m/s}$
• D. $22\text{m/s}$

Answer 1

The correct option is B $32\text{m/s}$

The velocity of the wall will not change after the collision.

Let $v$ be the velocity of the ball after collision in direction shown in figure.

For elastic collision;

Speed of separation = Speed of approach

$\Rightarrow v-10=12+10$

$\therefore v=32\text{m/s}$