A disc of mass 1 kg is connected to an ideal spring of force constant k on a 37° incline. It is released from rest as shown. Assuming sufficient friction for pure rolling, find the maximum friction force on the disc (in N).

Question

G1 Physics · Accepted Answer

Along the incline, for a solid disc rolling without slipping, translation and rotation give an effective inertia 3m/2. The static friction required is one-third of the net external force along the plane. At release the spring is unstretched, so the largest net force is mg sin37°=1×10×3/5=6 N. Therefore maximum friction=6/3=2 N.