1. The problem statement, all variables and given/known data the mass, M, of the disk is 20kg, the radius is r and the force applied, F, in the periphery of the disk is 9.8N. How much is the angular acceleration? If I add a mass (m1) of 1kg to the thread what will be the angular acceleration? 2. Relevant equations I think those are relevant to my problem: Moment of inertia of a disk: I=0.5*m*r^2 Torque=Force*radius*sin(tetha) angular acceleration=Torque/Moment of inertia 3. The attempt at a solution a) I=.5mr^2 ⇔I=2.5 Torque=9.8*0.5=4.9N*m angular acceleration=4.9/2.5 = 1.96 rad/s^2 I think this one is correct b) Since it was added another mass I tought that the total force would be F+T, tension being equal to the force of the mass*gravity (9.8). Then: I=2.5 Torque=9.8N*m angular acceleration=9.8/2.5=3.92 rad/s^2 The correct answer is 1.8 rad/s^2. any hints would be highly appreciated! Thanks. D.