A physics teacher throws a 6 kg dodgeball 17 m / s, hitting a 50 kg student, who is initially at rest on a skateboard. After hitting the student, the dodgeball rebound back left with a speed of 5 m / s.

before collision:

| p | ball = 102 kg m / s
| p | student = 0 kg m / s


after collision:

| p | ball =30 kg m / s
| p | student =