Question

A penny of mass m is placed on an old-school turntable at radius r from the center. At time t = 0, the turntable starts to spin up from rest at a constant angular acceleration ?Z.The coeffcient of friction between the penny and the turntable is µS.

A)  If m = 2.5 g, µS = 0.30, and ?Z = 1.00 rad/s2 , what is the minimal radius such that the penny begins to slip immediately at t = 0?

B)  If r = 15 cm and all other number are the same as (a) what is the time t at which the penny begins to slip?

C)Assume that the penny begins to slip as in part (B). When it begins to slip, the coeffcient of kinetic friction is µK = 0.20. What are the x and y components of the force of kinetic friction?

Answer 1