1. The problem statement, all variables and given/known data A solid ball of constant density, a hollow ball and a hoop have the same radius. They are simultaneously released to roll without slipping down the same ramp. Write the order in which they reach the bottom and justify your answer. 2. Relevant equations 3. The attempt at a solution The thing is, it's worth 7 marks..I have no idea what working i need to do! So as they fall, PE is converted into KE.. KE is translational and rotational.. so mgh = 1/2mv^2 + 1/2Iw^2 = 1/2mv^2 + 1/2 I (v/r)^2 where h is the height fallen so gh = 1/2v^2 + 1/2 I/m (v/r)^2... Now im guessing the I/m will be the most for the solid ball, then for the hollow ball and least for the hoop..so hoop arrives first, then hollow ball, then solid ball.. is this right? How can i justify it more rigorously?