Question

A metal ball is moving with velocity $10\text{m/s}$ in downward direction as shown in the figure. After collision with a surface having coefficient of restitution $\left(e\right)=0.6$, it rebounds back. Find the rebound velocity. (Assume the surface remains stationary)

• A. $6\text{m/s}$
• B. $10\text{m/s}$
• C. $60\text{m/s}$
• D. $0.06\text{m/s}$

Answer 1

The correct option is A $6\text{m/s}$

Given,
Speed of the metal ball before collision $\left(u_1\right)=10\text{m/s}$
Speed of the surface before collision $\left(u_2\right)=0\text{m/s}$
and speed of the surface after collision $\left(v_2\right)=0\text{m/s}$
Let the rebound speed of the ball be $v$.

Coefficient of restitution $\left(e\right)=0.6$
We know,
Coefficient of restitution $e=\frac{v_2-v_1}{u_1-u_2}=\frac{0-\left(v\right)}{-10-0}$
(Taking downward direction -ve)
$0.6=\frac{v}{10}\Rightarrow v=6\text{m/s}$