# A ball with a mass of #2 kg# is rolling at #4 m/s# and elastically collides with a resting ball with a mass of #4 kg#. What are the post-collision velocities of the balls?

##### 1 Answer

#### Answer:

The velocity of the first ball is

The velocity of the second ball is

#### Explanation:

In an elastic collision, we have conservation of momentum and conservation of kinetic energy.

The velocities before the collision are

The velocities after the collision are

and

Solving the above 2 equations for

and

Taking the direction as positive

Therefore,

Verificaition