I've successfully been able to simulate e pendulum (wow!). Now I want something slighly more complicated (at least I think it is). Suppose I take some 2d-object, for instance a square. Somewhere on the square I make a hole, and then I hang it on the wall on a nail. Then I move it a bit and let it fall (like a pendulum, but there is no string, instead the pivot is connected to the object itself). What is the physics behind the movements of this square?