Question
A block having mass $m$ collides with an another stationary block having mass $2\,m$. The lighter block comes to rest after collision. If the velocity of first block is $v$, then the value of coefficient of restitution will must be
✓
Answer
(a)
Since there is no external force acting on the system, the linear momentum of the system must be conserved.
Hence momentum before collision = momentum after collision
$\Rightarrow mv +0=0+(2 m ) v$
$v^{\prime}=\frac{v}{2}$
The coefficient of restitution $=$ Velocity of separation/Velocity of approach
$=\frac{ v }{ v }$
$=\frac{1}{2}$
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