Physics Project Ideas

[Vonriel]

trebuchets or catapults would be projectiles and circular motion.

This. A thousand times this. Both of these siege weapons utilize tons of physics goodies, and as part of your demonstration, you get to knock something to smithereens. You don't lose. (Sidenote: I loved the trebuchet project I had in my high school physics class)

If you need to back it up with physics, trebuchets fire their projectiles in an arc, and there is hopefully an awesome collision with some object at the end of said arc.