Question

A particle of mass $ m $ moving with velocity $ v $ collides with a stationary particle of mass $ 2m $ . The speed of the system, will be:

• A. $ 3v $
• B. $ \frac{v}{2} $
• C. $ v/3 $
• D. $ 2v $

Answer 1

Answer: (C)

Here $m_{1}=m$
$m_{2}=2 m$
$v_{1}=v$
$v_{2}=0$
Let the speed of the system after collison $=v$
Using the principle of conservation of linear momentum
$m_{1} v_{1}+m_{2} v_{2}=\left(m_{1}+m_{2}\right) v'$
$\Rightarrow v'=\frac{m v+2 m \times 0}{m+2 m}=\frac{m v}{3 m}=\frac{v}{3}$