Joe (**M = 60 kg**) rides his skateboard
(**m = 4 kg**) eastward at a speed of **1 m/s**.

- What is Joe's momentum?
- What is the skateboard's momentum?
- What is their total momentum?
- What is the velocity of their center of mass?

As he approaches the ice cream parlor, Joe notices a pretty
young woman sitting on the porch. He decides to make an
impressive entrance. At time **t = 0 s**, just as he
and the skateboard are passing the porch, he hops
backwards off the skateboard
so that he lands motionless on the ground.
The skateboard, on the other hand, shoots forward
and continues eastward at a speed **v**.

- What is Joe's momentum now, as he stands on the ground?
- What must the skateboard's momentum be now?
- What is the velocity
**v**of the skateboard? - At time
**t = 1 s**, where is the center of mass of Joe and the skateboard? Use a coordinate system centered on Joe. - At time
**t = 2 s**, where is the center of mass of Joe and the skateboard? - At time
**t = 3 s**, where is the center of mass of Joe and the skateboard? - What is the velocity of their center of mass?

Copyright © Michael Richmond. This work is licensed under a Creative Commons License.