1. The problem statement, all variables and given/known data A cylindrical rod 32.2 cm long has mass 0.919 kg and radius 1.54 cm. A 8.89 kg ball of diameter 11.3 cm is attached to one end. The arrangement is originally vertical with the ball at the top and is free to pivot about the other end. The acceleration of gravity is 9.8 m/s2 . After the ball-rod system falls a quarter turn, what is its rotational kinetic energy? Answer in units of J. At the same point, what is its angular speed? 2. Relevant equations K=.5Iw^2 3. The attempt at a solution I=1/3mL^2+2/5mR^2 Alright, I'm on the second part of the problem, having gotten the energy part. I cannot, however, for the stupid life of me, define this Ball-Rod system's moment of inertia in a fashion that gets me a reasonable answer. I'm wondering if I'm just missing something. If somebody could help me see it I can get the rest no problem. I also set it up in a way that it was just the rod with a big mass on the end of it, and that failed miserably. And I searched the forum for a similar problem, but the guy doing it had already found moment of inertia and didn't want to share.