Q. A ball of mass $10\ kg$ is moving with a velocity of $10\ m/s$. It strikes another ball of mass $5\ kg$ which is moving in the same direction with a velocity of $4\ m/s$. If the collision is elastic , their velocities after the collision will be, respectively
A) $6\ m/s,\ 12\ m/s$
B) $12\ m/s,\ 6\ m/s$
C) $12\ m/s,\ 10\ m/s$
D) $12\ m/s,\ 25\ m/s$
Explanation
(a) $v_{1} = \left( \frac{m_{1} - m_{2}}{m_{1} + m_{2}} \right)u_{1} + \left( \frac{2m_{2}}{m_{1} + m_{2}} \right)u_{2}$ and
$v_{2} = \left( \frac{2m_{1}}{m_{1} + m_{2}} \right)u_{1} + \left( \frac{m_{2} - m_{1}}{m_{1} + m_{2}} \right)u_{2}$
On putting the values $v_{1} = 6\ m/s$ and $v_{2} = 12\ m/s$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.