A 4-kilogram ball moving at 8 m/sec to the right collides with a 1-kilogram ball at rest. After the collision,

the 4-kilogram ball moves at 4.8 m/sec to the right. What is the velocity of the 1-kilogram ball?

Conservation of momentum: total momentum before = total momentum after

Momentum = mass x velocity

So before the collision:

4kg x 8m/s = 32

1kg x 0m/s = 0

32+0=32

Therefore after the collision

4kg x 4.8m/s = 19.2

1kg x βm/s = β

19.2 + β = 32

Therefore β = 12.8 m/s