A uniform disk is attached at the rim to a vertical shaft and is used as a cam. The disc has a diameter of 38 cm. The moment of inertia of the disk about the axis of the shaft is 7.5*10^-3 kg*m/s. The shaft rotates uniformly about its axis at 70 rpm. The mass of the disc is closest to: a.0.12 kg b. 0.092 kg c. 0.14 kg d. 0.18 e.0.16 kg I don’t know why the angular velocity is given. This is what I managed to do: Using parallel axis theorem, I_p = I_cm + M*d^2 = 0.5*M*r^2 + M*r^2 = 1.5*M*r^2 M = (I_p)/(1.5*r^2) = (0.0075 kg*m/s)/(1.5*.19 cm^2) = 0.1385 kg Thanks.