1. A ball of mass 0.544 kg is moving east with a speed of 3.90 m/s and collides head-on with a 0.272 kg ball at rest. Assume that the collision is perfectly elastic. After the collision, the 0.544 kg ball moves at 1.3 m/s.
What is the speed of the 0.272 kg ball after the collision?
2. A 0.300 kg hockey puck, moving east with a speed of 5.38 m/s, has a head-on collision with a 0.950 kg hockey puck that is initially at rest. Assume that the collision is perfectly elastic. After the collision, the 0.950 kg puck moves at 2.58 m/s to the east.
What is the speed of the 0.300 kg hockey puck after the collision?
Can anyone explain this to me? :( I figured out all the other questions on the homework, but these have me stumped.