A bead slides down along a piece of wire that is in the shape ofa helix. The helix lies on the surface of a vertical cylinder ofradius r, and the vertical distance between turns is d. (a)Ordinarily when an object slides downhill under the influence ofkinetic friction, the velocity-independence of kinetic frictionimplies that the acceleration is constant, and therefore there isno limit to the object’s velocity. Explain the physical reason whythis argument fails here, so that the bead will in fact have somelimiting velocity. (b) Find the limiting velocity. (c) Show thatyour result has the correct behavior in the limit of r → ∞.
