I am probably not taking the AP physics C tests, but I have the book from when I studied by myself for the AP physics B test, and it has all the Physics C stuff in there as well. Now, with that said, there is a section in rotational motion. Most of it makes perfect sense mathematically, but I just do not get conceptually how: I = rotational intertia M = mass r = radius I = M*r^2 That's like what, inertia at an area? It just seems to make such little conceptual sense. Does anyone have a better way of thinking about rotational inertia?