Circular motion, coin on a rotating disk

[fallingforfandoms]

Homework Statement

A small button placed on a horizontal rotating platform with diameter 0.520 m will revolve with the platform when it is brought up to a speed of 41.0 rev/min , provided the button is no more than 0.250 m from the axis.
How far from the axis can the button be placed, without slipping, if the platform rotates at 61.0 rev/min ?

Relevant Equations

In the previous part of the question we found mu = 0.47
mu(v^2/r)=g

First I tried to convert V = 61 rev/min to linear velocity.
frequency = 61 rev / 60 sec = 1.017 rev/sec
time = 1/f = 0.983 s
V = 2(pi)r/t = 0.52*pi/0.983= 1.662 m/s
From there I tried to find the maximum radius the coin could be at by using mu(v^2/r)=g
r = mu(v^2)/g
r= 0.47(2.76)/9.8
r= 0.13 m
That seems to be wrong though, so now I am a bit lost.

 

[kuruman]

From there I tried to find the maximum radius the coin could be at by using mu(v^2/r)=g

Where did you get this equation? Check your source.

 

[TSny]

Welcome to Physics Forums!

Relevant Equations:
mu(v^2/r)=g

This formula as written is not correct. Check it.

frequency = 61 rev / 60 sec = 1.017 rev/sec
time = 1/f = 0.983 s

OK. (The time here is the period of revolution of the platform when it is rotating at 61 rpm.)

V = 2(pi)r/t = 0.52*pi/0.983= 1.662 m/s

Did you let r equal the radius of the platform in this calculation? If so, wouldn't V then equal the linear speed of a point at the outer edge of the platform? Is that the speed that you want?