Question

a 4 kilogram ball moving at 8 meters per second to the right collides with a 1 kilogram ball at rest. After the collision, the 4 kilogram ball moves at 4.8 meters per second to the right. What is the velocity of the 1 kilogram ball?

Answer 1

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