# A ball with a mass of #6 kg# moving at #3 m/s# hits a still ball with a mass of #8 kg#. If the first ball stops moving, how fast is the second ball moving?

##### 2 Answers

Momentum is conserved, so if the first ball stops from the collision, then the second ball will have the same momentum as the first ball did.

#### Explanation:

The momentum of the firs ball is:

If that ball stops, then all the momentum is transferred to the second ball,

Solve for

(6 X 3)/8 = 2.25 m per sec in the same direction

#### Explanation:

Use law of conservation of momentum.

Momentum = mass X Velocity

Ball 1 has mass

Ball 2 has mass

Initial momentum =

Ball 1 has final velocity

Ball 2 has final velocity

Final momentum =

Initial momentum = Final momentum

As initial velocity of Ball 2 is 0 before collision and velocity of Ball 1 is 0 after collision.