Easy question that I'm not getting?? 1. The problem statement, all variables and given/known data A small ball with mass 1.40 kg is mounted on one end of a rod 0.850 m long and of negligible mass. The system rotates in a horizontal circle about the other end of the rod at 5020 rev/min. Calculate the rotational inertia of the system about the axis of rotation. 2. Relevant equations I=MR2/3 3. The attempt at a solution Inertia for a rod spinning at one end = MR2/3, so I did that and got .337, but that wasn't the correct answer. What am I doing wrong?