Question

A block of mass $m$ moving at a velocity $v$ collides with another block of mass $2m$ at rest. The lighter block comes to rest after collision. Find the coefficient of restitution.

• A. $\frac{1}{2}$
• B. $1$
• C. $\frac{1}{3}$
• D. $\frac{1}{4}$

Answer 1

The correct option is A $\frac{1}{2}$

From conservation of linear momentum we can see that velocity of $2m$ will become $\frac{v}{2}$ after collision (as mass is doubled).

Now,

$e=\frac{\text{Relative velocity of seperation}}{\text{Relative velocity of approach}}$

$=\frac{v/2}{v}=\frac{1}{2}$