# Homework Help: Find the Coefficient of Friction Given Frequency

1. Nov 11, 2008

### CoffexCream

1. The problem statement, all variables and given/known data
A rubber Eraser is placed on a cardboard record on a turntable. The turntable is set to 33 1/3 rotations per minute. what is the max radius for the eraser to be placed without slipping. but first calculate the coefficient of friction. You will not be given mass or radius of the 'record'

2. Relevant equations
ac=V2/r
ac= 4pi2rf2
us=Tan $$\theta$$

3. The attempt at a solution
no idea as to how to get this...i cant seem to make any connections...

$$\mu$$Fn=m x ac
$$\mu$$=Tan $$\theta$$
Tan $$\theta$$=m x ac
Tan $$\theta$$= ac / g
Tan $$\theta$$= 4$$\pi$$^2rf^2

then acceleration can be either of the centripetal acceleration equations but the n i get totally stuck because i cant get rid of r xD

Last edited: Nov 11, 2008
2. Nov 11, 2008

### BishopUser

perhaps the fact that it is a rubber eraser and a cardboard turntable means something. i would check your textbook for useful tables

3. Nov 11, 2008

### CoffexCream

unfortunately this question was randomly made by my teacher and its not in the textbook >.>