Angular Momentum (Not the usual Turntable Question)

[divineyang]

Homework Statement

A dog of mass m is standing on the edge of a stationary horizontal turntable of totational inertia I and radius R. The dog walks once around the circumference of the turntable.

What fraction of a full circle does the dog's motion make with respect to the ground? Express your answer in terms of m, I and R. Ignore friction at the axle of the turntable.

Homework Equations

Conservation of angular momentum

The Attempt at a Solution

The turntable will rotate in the opposite direction as motion of the dog. Hence initial angular momentum = final angular momentum = zero.

Final angular momentum = Angular momentum of the dog wrt the ground - angular momentum of the table wrt the ground = 0

Is it correct so far?

I'm not sure as to how to proceed after that. Can anyone help me on this? Thanks!

 

[zorro]

I don't think that will lead you to the right answer. We don't need to find any final velocities (so I think no use of applying COAM).
I will give you a hint.
Consider the torque acting about the point of hinge (centre of the table) by the force-pair which causes the dog to move forward.