A 80 g disk sits on a horizontally rotating turntable. The turntable makes exactly3revolutions each second. The disk is located 15 cm from the axis of rotation of the turntable.
a) What is the frictional force acting on the disk? N?
b) The disk will slide off the turntable if it is located at a radius larger than 21 cm from the axis of rotation. What is the coefficient of static friction?