1. The problem statement, all variables and given/known data A wheel is turning initially at 1200 turns/min and stops in 4 min because of friction. If we add a supplementary torque of 300 N*m, the wheel stops in 1 min. a) What is the moment of inertia of the wheel? b) What is the torque of friction? 2. Relevant equations Torque = alpha * I time = w/alpha f = ucF Torque = -fR 3. The attempt at a solution I figured i'd start by converting the 1200 turns/min into rad/sec (1200 *2pi)/60 = 126 rad/sec (this gives me angular speed - w) Then I figured i'd find the angular acceleration using the angular speed that I just found with the time it takes to stop (in this case its 4min or 240seconds). alpha = 126/240 = 0.525 Now at first I thought I could just substitute these in the equation Torque = alpha * I but it doesn't work out. I then realised that they are saying that there is a SUPPLEMENTARY torque and it then stops in 1min. I thought it would then be something like "initial torque + 300 = something...". Does that make any sense? Any help to clear this up would be appreciated!