A disk with moment of inertia I relative to a vertical axis through its center is dropped onto another disk with moment of inertia equal to 2I which is rotating with angular velocity. Find the final angular velocity in terms of.

0.66 times the original one

Explanation:

A disc of moment of inertia 2I is rotating with angular speed ω. Now another disc of moment of inertia I dropped on it and the new angular velocity is ω'.

By use of conservation of angular momentum

2I x ω = (2I + I) x ω'

ω' = 2ω/3

ω' = 0.66 ω

Thus, the new angular velocity becomes 0.66 times the original one.