1. The problem statement, all variables and given/known data A motor accelerates more and more a wheel without friction. It is supposed the belt gives forces F1 and F2 at only one point. http://imageshack.com/a/img674/1437/Uh0XIp.png [Broken] 2. Relevant equations None 3. The attempt at a solution I would like to know if I drawn all forces: http://imageshack.com/a/img674/2809/o4uI79.png [Broken] 1) Is it correct ? 2) The motor is turning clockwise at ω, so the wheel is turning at ωR1/R2 ? 3) The motor needs to give F1R1ωt, so the wheel receives F2R2ωR1/R2=FR1ωt because |F1|=|F2|, correct ? 4) The sum of forces on the belt is F3-F4, if the motor accelerates this could say the belt is accelerating too, then F3 must be higher than F4, so F1 must be higher than F2 (the absolute value not the vector) ? I'm not sure, if F2 is lower the torque on the wheel is lower too, so the last calculation is false ?