Question

Two balls of mass $m$ and $M$ are moving with horizontal speed of $16\text{m/s}$ in the direction as shown in the figure. If $m<<M$, then for one dimensional elastic collision, the speed of lighter ball after collision will be

• A. $48\text{m/s}$
• B. $16\text{m/s}$
• C. $32\text{m/s}$
• D. $0\text{m/s}$

Answer 1

The correct option is A $48\text{m/s}$

Given, Velocity of mass $m$, $u_1=+16\text{m/s}$
Velocity of mass $M$, $u_2=-16\text{m/s}$

$\Rightarrow$In case of elastic collision, when $m<<M$, the velocity of heavier mass will remain constant.

Therefore velocity of masses after collision is shown below:


$\Rightarrow$for perfectly elastic collision :
speed of separation $=$ speed of approach
$(v-16)=(16+16)$
Or, $v-16=32$
$\therefore v=48\text{m/s}$