Q. A 10 kg object collides with stationary 5 kg object and after collision they stick together and move forward with velocity 4 ${ms}^{- 1}$.what is the velocity with which the 10 kg object hit the second one?
A) 4 ${ms}^{- 1}$
B) $6\ {ms}^{- 1}$
C) $10\ {ms}^{- 1}$
D) $12\ {ms}^{- 1}$
Explanation
(b) $m_{1}u_{1} + m_{2}u_{2} = \left( m_{1} + m_{2} \right)v$
$\therefore$ $10 \times u_{1} + 5 \times 0 = (10 + 5) \times 4$
Or $u_{1} = \frac{15 \times 4}{10} = 6ms^{- 1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.