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## Homework Statement

A potter’s wheel—a thick stone disk of radius 0.500 m

and mass 100 kg—is freely rotating at 50.0 rev/min.

The potter can stop the wheel in 6.00 s by pressing a

wet rag against the rim and exerting a radially inward

force of 70.0 N. Find the effective coefficient of kinetic

friction between wheel and rag

## Homework Equations

## The Attempt at a Solution

Actually, I could get the answer using angular acceleration and torque, but I could do the same thing with Newtonian Laws and I want to know why.

Tangential velocity of the wheel:

50 rev/ min = 2.618 m/s

u = 2.618 m/s, v = 0, a = ?, t = 6

v = u + at

0 = 2.618 + 6a

a = 0.436 m/s^2

Deceleration force

F = ma = (100)(0.436) = 43.6N

The friction coefficient

43.6 = (coefficient)(70)

coefficient = 0.623, which is exactly the double of the correct answer.

Thanks!