Kidinu: What's this?
Katyayana: Just four balls bouncing around.
Kidinu: Did you see that you can stop the motion by moving the cursor off the image?
Katyayana: So you can. What happens if you click on the image?
Kidinu: Ah, that's interesting. Can you move them, too?
Katyayana: Right over each other.
Kidinu: Look, you can toss them, too.
Katyayana: Yep. Let's see how fast I can get them to go.
Kidinu: Whoa, slow it down, will you?
Katyayana: Hey, where'd that one go? I tossed it right out of the circle.
Kidinu: It's back now.
Katyayana: What do you think the physics is behind bouncing balls?
Kidinu: I'm sure it can't be too complicated.
David E. Joyce
Department of Mathematics and Computer Science
Clark University
Worcester, MA 01610