A 5-kg moving at 6 m/s collided with a 1-kg ball at rest. The ball bounce off each other and the second ball moves in the same direction as the first ball at 10 m/sec. What is the velocity of the first ball after the collision?

Given :

A 5-kg moving at 6 m/s collided with a 1-kg ball at rest.

The ball bounce off each other and the second ball moves in the same direction as the first ball at 10 m/sec.

To Find :

The velocity of the first ball after the collision.

Solution :

We know, by conservation of momentum :

Putting all given values with directions ( one side +ve and other side -ve ).

Therefore, the velocity of first ball after the collision is 4 m/s after in opposite direction.

Hence, this is the required solution.

b would be the answer