Conservation of angular momentum book problem

[joahe]

Homework Statement

2. The attempt at a solution

I set the initial angular momentum of the disk = to the sum of : rod's angular momentum, angular momentum of disk, rod's center of gravity and disk's center of gravity. With the reference point being at B.

Why is the velocity of the rod's center of gravity not included in the solution?

Thanks for any and all help.

 

[JeremyG]

Why is the velocity of the rod's center of gravity not included in the solution?

It has already been taken into account because the moment of inertia used for the rod was 1/3ML². If the MOI used was 1/12ML² then you can add the angular momentum contribution from the velocity of the rod's center of mass. This is essentially the application of the Parallel-Axis Theorem.

Hope this helps!

 

[joahe]

It has already been taken into account because the moment of inertia used for the rod was 1/3ML². If the MOI used was 1/12ML² then you can add the angular momentum contribution from the velocity of the rod's center of mass. This is essentially the application of the Parallel-Axis Theorem.

Hope this helps!

Thanks Jeremy, that completely clears things up. Cheers!