Posted by Kelsey on .
A potter's wheel having a radius 0.55 m and a moment of inertia 11.6 kg·m2 is rotating freely at 55 rev/min. The potter can stop the wheel in 8.0 s by pressing a wet rag against the rim and exerting a radially inward force of 66 N. Find the effective coefficient of kinetic friction between the wheel and the wet rag.
I do not even know where to start on this problem.

physcs 
drwls,
I w /8.0 s = angular momentum decrease rate = torque = friction force* radius
w is the initial angular velocity
= 55*2*pi/60 = 5.76 rad/s
I is the moment of inertia
Solve for the friction force and use that and the applied normal force to get the coefficient of kinetic friction.