Question

A ball of mass $5\text{kg}$ moving at speed $2\text{m/s}$ makes a head on collision with an identical ball at rest. The velocities of the balls after the perfectly elastic collision between them are respectively:-

• A. $1\text{m/s},1\text{m/s}$
• B. $0\text{m/s},2\text{m/s}$
• C. $1.2\text{m/s},0.5\text{m/s}$
• D. $1.5\text{m/s},0.2\text{m/s}$

Answer 1

The correct option is B $0\text{m/s},2\text{m/s}$


Given, the collision is perfectly elastic, $e=1$.
Since $m_1=m_2$ and $e=1$,
the balls will exchange their velocity.
Therefore, final velocity of $m_1,v_1=0\text{m/s}$
& final velocity of $m_2,v_2=2\text{m/s}$