A solid disk of radius 23.4 cm and mass 1.45 kg is spinning at 43.1 radians per second. A solid cylinder of radius 12.1 cm and mass 3.33 kg is not spinning. The cylinder is dropped into the center of the spinning disk. After a short time friction has caused both objects to engage and turn in the same direction and rate.
a) Determine final rotational direction and angular velocity of the system?
b) Determine the change in mechanical energy of the system?
The Attempt at a Solution
i found a) 26.7 rad/s
I am having trouble finding the mechanical energy I don't know which equation I should use. I tried using