Q. A particle of mass m moving with horizontal speed $6\ m/sec$ as shown in figure. If $m < \ < M$ than for one dimensional elastic collision, the speed of lighter particle after collision will be
A) $2m/sec$ in original direction
B) $2m/sec$ opposite to the original direction
C) $4m/sec$ opposite to the original direction
D) $4m/sec$ in original direction
Explanation
(a) $v_{1} = \left( \frac{m_{1} - m_{2}}{m_{1} + m_{2}} \right)u_{1} + \frac{2m_{2}u_{2}}{m_{1} + m_{2}}$
Substituting $m_{1} = 0,\ v_{1} = - u_{1} + 2u_{2}$
$\Rightarrow v_{1} = - 6 + 2(4) = 2\ m/s$
$i.e.$ the lighter particle will move in original direction with the speed of $2\ m/s$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.