A body of mass `3 kg` moving with a velocity of `4 m//s` towards left collides head on with a body of mass `4 kg` moving in opposite direction with a velocity of `3 m//s`. After collision the two bodies stick together and move with a common velocity which is

Options

A. zero
B. `12 m//s` towards left
C. `12 m//s` towards right
D. `12/7` m//s towards left

Answer

A

Explanation

Initial momentum `3xx4=4xx(-3)=0`
Final momentum will also be zero but both stick together, hence both come at rest.