Hi. Ok, I've given this question already soooooo much time and I simply cannot solve it. 1. The problem statement, all variables and given/known data There's a circular surface that's holding still (like a bowl), with radius R, and a ball, with radius r, on it. The ball is rolling without sliding. The mass of the ball and it's moment of intertia are given. 1. First question - express the relation between W, which is the angular velocity of the ball, and "d(theta)/dt", where "theta" is the angle formed in any time between the "main axis of the bowl" and the radius streaching to the ball. 2. Second question - find the relation between W and theta(not theta dot as before), given that the ball starts it's movement at hight "h" above the surface. 3. Third and last - given that the ball is oscillating in small values of theta, what is the period time of the harmonic movement? (they give a hint: differentiate (with t) the function we found in the last questions - W(theta), find a "movement equation", and compare it to the "harmonic oscillation" classic equation. !!! 3. The attempt at a solution 1. I Think I did that - w(t)* r = (theta dot) * R. 2.Ok, here I used mechanical energy cons. and after some effort found a pretty complex relation between W and theta. I won't specify it here but it has square root and all :) 3. Here's the real trouble: From their hint I think I need to find d(W(t))/dt ? So I can do that using the "chain law" (I'm not sure if that's the name) and take the derivitive of t like this: d(W(t))/dt = d(W(theta))/d(theta) * d(theta)/d(t) After doing that, using the relations I got in the previous questions, I get a non-linear, second-order diffrential equation. Not solvable of course. The excercise is a pretty classic one, just a plate with a ball rolling on it - but I still find it very complicated! Maybe I'm over-complicating things? I'm desprate for help :-\ Thank you very much for reading.