In an isolated system the moment of inertia of a rotating object is doubled. What happens to angular velocity of the object?

A disk is spinning at a rate of 10 rad/s. A second disk of the same mass and shape, with no spin, is placed on top of the first disk. Friction acts between the two disks until both are eventually traveling at the same speed. What is the final angular velocity of the two disks?

Explain, in terms of conservation of angular momentum, why comets speed up as they approach the sun.

A particle attached to a string of length 2 m is given an initial velocity of 6 m/s. The string is attached to a peg and, as the particle rotates about the peg, the string winds around the peg. What length of string has wound around the peg when the velocity of the particle is 20 m/s?

Two balls, one of mass 1 kg and one of mass 2 kg, are confined to move in a circular track. They move at an equal velocity, v, in opposite directions on the track and collide at a point. The two balls stick together. What is the magnitude and direction of the velocity of the balls after the collision, in terms of v?