Question

A thin uniform cylindrical turntable of radius 2.1 m and mass 18 kg rotates in a horizontal plane with an initial angular speed of 8 rad/s.
The turntable bearing is frictionless. A clump of clay of mass 5.5 kg is dropped onto the
turntable and sticks at a point 0.9 m from the point of rotation.
Find the angular speed of the clay and turntable.
Answer in units of rad/s
The rotational
inertia of a disc is 1/2(MR-squared).

OK... so i am "supposedly" doing everything right, by using an elastic equation and substituting mass with inertia and velocity with angular velocity... but i keep getting the same answer... 7.575 rad/s and its wrong...

Answer 1

It's an inelastic conservation of angular question.
I omegai = I omegaf (turntable)+ I omegaf (Clay, I = mr^2)

And obviously omegaf is the same for both.