A 4.0-kilogram ball moving at 8.0 m/s to the right collides with a 1.0-kilogram ball at rest. After the collision, the 4.0-kilogram ball moves at 4.8 m/s to the right. What is the velocity of the 1-kilogram ball?
Use conservation of momentum. Check to see if your answer makes sense. A heavy ball moving right hits a stationary ball. Afterwards they should both be moving right and the lighter ball should be moving faster.