Kidinu: Okay, fine. What happens, though, to the velocity when the ball hits the wall?
Ahmes: You're asking what the new velocity will be? You can probably answer the question yourself when the wall is straight, can't you?
Kidinu: Well, sure. It just goes off in the opposite direction.
Ahmes: Which means...?
Kidinu: Maybe not the opposite direction. That would mean it goes back the way it came. I really meant something like this. [Kidinu draws a picture.]
Ahmes: So what you're saying is that the angle of incidence equals the angle of reflection. Is that so?
Kidinu: Yes, that's it.
Katyayana: That's fine if the wall is straight, but these walls are curved.
Ahmes: It's almost the same thing, that is, it's as if the place where the ball hits the wall is straight.
Kidinu: I haven't seen much physics yet.
Ahmes: Not that much is needed, so far. But collisions between balls is more complicated.
David E. Joyce
Department of Mathematics and Computer Science
Clark University
Worcester, MA 01610
