Question

A circular disk of mass 0.3 kg and radius 40 cm, initially not rotating, slips down a thin spindle onto a turntable (disk) of mass 1.7 kg and the same radius, rotating freely at 3.1 rad/s.
a) Find the new angular velocity of the combination;
A circular disk of mass 0.3 kg and radius 40 cm, initially not rotating, slips down a thin spindle onto a turntable (disk) of mass 1.7 kg and the same radius, rotating freely at 3.1 rad/s.

a) Find the new angular velocity of the combination;
rad/s

b) The change in the kinetic energy?

c) If the motor is switched on after the disk has landed, what is the constant torque needed to regain the original speed in 3.9 s?
N*m