Question

A ball falls from a height of 5m and strikes a lift which is moving in the upward direction with a velocity of 1m/s, then the velocity with which the ball rebounds after collision will be –

• A. 11 m/s downwards
• B. 12 m/s upwards
• C. 13 m/s upwards
• D. 12 m/s downward

Answer 1

Answer: (B)

12 m/s upwards

Answer 2

Velocity after a fall of 5m = $\sqrt{2 \times 10 \times 5}$ = 10 m/s

${\overline{v}}_{1} - {\overline{v}}_{2}$= e (${\overline{u}}_{2} - {\overline{u}}_{1}$)

$v_{1} - 1$ = 1 – (–10) = 12 m/s