# Potters wheel coefficient of kinetic friction

1. Mar 25, 2012

### arogers5

1. The problem statement, all variables and given/known data

A potter's wheel having a radius 0.49 m and a moment of inertia of 10.6 kg · m2 is rotating freely at 52 rev/min. The potter can stop the wheel in 5.5 s by pressing a wet rag against the rim and exerting a radially inward force of 68 N. Find the effective coefficient of kinetic friction between the wheel and the wet rag.

2. Relevant equations

I = .5mr^2

3. The attempt at a solution

I wasnt sure where to start. I know how to solve for the mass of the wheel, I know the moment of inertia formula and I know that the coefficient of kinetic friction is equal to μN. I drew a picture of the situation but am not sure how the moment of inertia and the decelleration are going to relate to the force that is applied.

2. Mar 25, 2012

### tiny-tim

welcome to pf!

hi arogers5! welcome to pf!

first do the geometry, then the physics

the geometry is the angular acceleration: find it from the given initial and final speeds, and the time

then use the moment of inertia to find the total torque

then subtract to find the friction