Question

A heavy steel ball of mass greater than $1kg$ moving with a speed of $2m$ $se{c}^{-1}$ collides head on with a stationary ping-pong ball of mass less than $0.1gm$. The collision is elastic. After the collision the ping-pong ball moves approximately with speed

• A. $2m$ $se{c}^{-1}$
• B. $4m$ $se{c}^{-1}$
• C. $2\times {10}^{4}m$ $se{c}^{-1}$
• D. $2\times {10}^{3}m$ $se{c}^{-1}$

Answer 1

The correct option is B $4m$ $se{c}^{-1}$

Since steel ball is much heavier than ping Pong ball, and collision is elastic.

$e=1$

$e=\frac{v-2}{0-2}$

Where $v$ is the velocity of ping Pong ball.

$1=\frac{v-2}{0-2}$

$⟹v=4m/s$