I am trying to spec out a motor to move a disc on a bearing, the disc has a mass on it weighing 20,000lbs. The diameter of the disc is 3.33ft. Angular acceleration of 0.1047 rad/s^2 to 3RPM. I am assuming coefficient of friction of 0.5. 1. Can I use the assumption that the mass on the disc doesn't matter much for my calculation and use that weight (20,000lbs) for my I=(1/2)*m*r^2? 2. Is the 0.5 coefficient pretty conservative in general for a disc on a bearing? If so, I am getting I=55778 T=I*a*(coefficient of friction) = 2920 HP = 1.668 This sound about right? Thanks for any help.