This is rewording of a question on a test I've just done. A vinyl record on a turntable has radius R=0.15 m, mass M=1.5 kg. The angular speed is reduced from 33.3 rev per minute to zero as a result of an applied torque, in 7 seconds. Moment of inertia given as I=1/2 M R^2 Calculate a) angular speed b) Magnitude of angular deceleration c)Moment of inertia d) Magnitude of applied torque. My attempt. a) angular speed, w = 33.3 x 2 pi / 60 s = 3.5 rad s^-1 b) a= dw/dt = 3.5/7 = 0.50 rad s^-2 c) I = 0.5 x 1.5 kg x 0.15^2 = 0.017 kg m^2 d) angular momentum L = I w = 3.5 rad s^-1 x 0.017 kg m^2 = 0.059 torque = dL/dt = 0.059/7 s = 0.0084 N m Does this look right (ignore any rounding errors). Seems quite a small magnitude for the torque. Anyway, thanks for any help!