Question

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?

Answer 1

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 :

$m_1u_1 + m_2u_2 = m_1v_1 + m_2v_2$

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

$5\times 6 + 1\times 0 =5 \times v_1 + 1\times 10\\\\5v_1=10-30\\\\v = -4 \ m/s$

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

Hence, this is the required solution.