Please help me do this physics problem? i dont have a clue how to do it?

Question

A coin is placed 31cm from the center of a horizontal turntable, initially at rest. The turntable then begins to rotate. When the speed of the coin is 130 cm/s (rotating at a constant rate) the coin just begins to slip. (the acceleration of gravity is 980 cm/s^2).

1) what is the coefficient of static friction between the coin and the turntable?

Answer 1

The normal force Fn = g*m. The centripetal force Fc = m*v^2/r. Slip happens when Fc = Fn*coefficient of friction mu, so mu = Fc/Fn = v^2/(g*r).