Centripetal Force (RPM Question)

[McKeavey]

Homework Statement

A coin is placed 18cm from the axis of a rotating turntable of variable speeds. If the coefficient of friction is 0.68, what is the maximum r.p.m that the coin can handle before sliding off?

Homework Equations

This is basically what I need..
I know there's mv^2/r
But which equation do I need for RPM questions?

The Attempt at a Solution

None at the moment, not sure of the equation I'm supposed to use :S

 

[PeterO]

Homework Statement

A coin is placed 18cm from the axis of a rotating turntable of variable speeds. If the coefficient of friction is 0.68, what is the maximum r.p.m that the coin can handle before sliding off?

Homework Equations

This is basically what I need..
I know there's mv^2/r
But which equation do I need for RPM questions?

The Attempt at a Solution

None at the moment, not sure of the equation I'm supposed to use :S

As well as mv²/r there is 4∏²rm/T² where T = period

Since frequency is 1/T that would mean 4∏²rmf²

frequency means revolutions per second. r.p.m is revolutions per minute.