The spool of wire has an inner radius r and an outer radius R. The angle between

Question:

The spool of wire has an inner radius r and an outer radius R. The angle θ between the applied force and the horizontal can be varied. Show that the critical angle for which the spool does not roll is given by
If the wire is held at this angle and the force increased, the spool will remain stationary until it slips along the floor.