A 70-g disk sits on a horizontally rotating turntable.The turntable makes 4 revolution each second. The disk is located 12cm from the axis of rotation of the turntable.
a. What is the frictional force acting on the disk?
b. The disk will slide off the turntable if it is located at a radius larger than 18 cm from the axis of rotation. What is the coefficient of static friction?