Answer the following questions in Notes on your handheld computer.

1. Rank your cart and at least two others in order of how they did on the friction test. What differences in the carts might account for the results?

2. When your cart is moving, it has energy of motion. What factors do you think affect its energy? When your cart slows down and stops, where does the energy go? What about when the cart hits something?

3. What happened to the motion of the acrobat when the cart slowed down? What about when the cart hit something?

4. What are the sources of friction for these carts? Do you think air resistance plays a role? How could you find out?

5. How does a vehicle behave when there is very little friction? Does it take a lot of force to get it going? To keep it going?