(adsbygoogle = window.adsbygoogle || []).push({}); [SOLVED] Circular Motion Problem

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

A coin is placed 0.11 meters from the center of a rotating turntable. The speed of the turntable is slowly increased; the coin remains fixed on the turntable until 36 rpm is reached and the coin slides off. What is the coefficient of the static friction between the coin and the turntable?

2. Relevant equations

T= (2*pi*r)/v

T= tau, which I believe is revolutions per second

(Fnormal)(coefficient of static friction) = (Ffriction)

Ac = v^2/r

Ac = centripetal acceleration

3. The attempt at a solution

First I divided the rpm by 60 to get the revolutions per second, or 0.6 rps. I put that as T in the tau equation and solved for v: 1.15 m/s. Then, because I was unsure of where to go next because of a lack of a mass value, I did something sort of stupid where I solved for Ffriction using the wrong equation or something (I'm reviewing an old test, not sure what my rationale was):

F = (coefficient)(Fnormal)

except for Fnormal part I did mass times centripetal acceleration

F = (coefficient)(m)(v^2/r)

and got a coefficient of 0.8123, which was wrong. At least I'm getting close; I believe coefficients of static friction must be less than 1.

Can anyone please give me a hand?

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# Homework Help: Circular Motion Problem

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