Friction between rotating objects

[Telanor]

In physics, we learned about friction between one object sliding across another, but when we got to torque and angular velocity, etc, there was never any mention of how to calculate friction between 2 objects rotating in place. Say you have a plate on top of a table and it is rotating about the center of the plate. How would you calculate the friction between the plate and the table if the coefficient of friction is known?

 

[malawi_glenn]

change to spherical coordinates and integrate over the surface.

 

[tiny-tim]

change to spherical coordinates and integrate over the surface.

Yes … specifically, if you divide the plate into concentric ring-shaped bits, each bit of length 2πa will have the same behaviour under friction as a straight rod of the same mass and of length 2πa.

 

[Telanor]

Thank you guys for your help. I am going to see if I can figure out this problem I was working on now