Euclidean Geometry in Physics I've started tutoring my 13 year old niece in math.  She learning geometry this year (it's a year-round school).  Obviously, it'll just be basic Euclidean geometry -- though I might try to get to a little non-Euclidean stuff at the end.
Anyway, she says she's interested in physics (how she can interested in something she's never studied IDK, but I guess it's good she's interested in science).  I was trying to think up ways to teach her some physics principles through geometry.  Unfortunately, without calculus, the only physics I can think of that uses geometry is the center of mass of an object.
Are there any other physics principles/ problems I could go over if all she knows is some basic algebra and geometry?

I am a fan of collisions.  Get some simple euclidean shapes (billiard balls, or dice on ice) and show her how to calculate the angles that they'll move in after hitting each other.
