Question

A ball is moving with velocity $10m/s$ in downward direction as shown in figure. After collision with fixed surface having coefficient of restitution $e=0.5$, it rebounds back with velocity $v\text{m/s}$. Find the value of $v$. (Neglect all external forces)

• A. $5\text{m/s}$
• B. $10\text{m/s}$
• C. $8\text{m/s}$
• D. $15\text{m/s}$

Answer 1

The correct option is A $5\text{m/s}$


As surface is fixed.
$\therefore$velocity of the surface before collision $\left(\overrightarrow{u_2}\right)=0\text{m/s}$
Velocity of surface after collision $\left(\overrightarrow{v_2}\right)=0\text{m/s}$

We know that:
Coefficient of restitution, $\left(e\right)=\frac{v_2-v_1}{u_1-u_2}=\frac{0-\left(v\right)}{(-10)-0}$
(Taking upward velocity + ve)
$\Rightarrow 0.5=\frac{v}{10}\Rightarrow v=5\text{m/s}$