Another way of stating it: When you have leaves in a (cylindrical) tea cup, if you rotate the cup (eg clockwise), the leaves largely stay in place relative to the table, but spin clockwise a little. What factors go into determining how much force (spin? torque?) transfers to the tea leaves (or to a neutrally buoyant object inside the cup)
I'm looking for highly simplified mechanics that can be translated into real-time rigid-body 2D physics for a video game (eg circles containing neutrally-buoyant specimens of various shapes). Having the circles bounce around like billiard balls is easy enough but I have no idea how to make them appear to be specimen-filled.
Any help is appreciated as I have little clue what to search for. I'm trying to avoid complex/super-realistic models/simulations (eg one that would contain many particles), but I'd be interested in the physics of it all, all the same.