What is the coefficient of static friction between the button and the platform?

What is the coefficient of static friction between the button and the platform?

A small button placed on a horizontal rotating platform with diameter 0.326 m will revolve with the platform when it is brought up to a rotational speed of 42.0 rev/min, provided the button is a distance no more than 0.144 m from the axis.

centripetal force = friction

mrω^2 = μmg

rω^2 = μg

(0.144 m)[(42.0 rev/min)(2π rad/rev)(min / 60 s)]^2 = μ(9.81 m/s^2)

μ = 0.284

What is the coefficient of static friction between the button and the platform?

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