A ball is moving with velocity `2 ms^(-1)` towards a heavy wall moving towards the ball with speed `1 ms^(-1)`, as shown. Assuming collision to be elastic, the velocity of the ball immediately after the collision (in `ms^(-1)`) is

Options

A. 2
B. 3
C. 4
D. 5

Answer

C

Explanation

The speed of wall will not change after the collision.
So, let v be the velocity of ball after collision.
Since collision is elastic, e=1.
`therefore` relative velocity of separation=relative velocity of approach.
`v - 1 = 2 + 1 implies v = 4 ms^(-1)`