Question

A ball is dropped on the floor from a height of 10 m. It rebounds to a height of 2.5 m. If the ball is in contact with the floor for 0.01 sec, the average acceleration during contact is

• A. $\frac{2100m}{{sec}^2}$ downwards
• B. $\frac{2100m}{{sec}^2}$ downwards
• C. $\frac{1400m}{{sec}^2}$
• D. $\frac{700m}{{sec}^2}$

Answer 1

The correct option is B $\frac{2100m}{{sec}^2}$ downwards

Velocity at the time of striking the floor
u=$\sqrt{2g{h}_1}=\sqrt{2\times 9.8\times 10}$=14 m/s
Velocity with which it rebounds.
v=$\sqrt{2g{h}_2}=\sqrt{2\times 9.8\times 2.5}$=7 m/s
$\therefore$Change in velocity $△v=7-(-14)=21m/s$
$\therefore$ Acceleration= $\frac{△v}{△t}=\frac{21}{0.01}=2100m/s^2$ upwards