Starting from rest, a 12-cm-diameter compact disk takes 3.0 s to reach its operating angular velocity of 2000 rpm. Assume that the angular acceleration is constant. The disk’s moment of inertia is . a. How much torque is applied to the disk? b. How many revolutions does it make before reaching full speed?

Solution Here we have first note down the given data: Radius of the disk=d/2=12 cm/2=0.060 m Initial angular velocity (w ) 0 0 rad/s Final angular velocity(w) = 2000 rpm,we must converted into SI units. w = (2000 rpm)(2/60) rad/s r =209.4 rad/s The compact disk is a rigid body.rotating about its center,the initial angular velocity w =00 rad/s and final angular velocity w = 209.4 rad/s. a....