A potter's wheel having a radius 0.55 m and a moment of inertia 13.3 kgm2 is rotating freely at 50 rev/min. The potter can stop the wheel in 4.

A potter's wheel having a radius 0.55 m and a moment of inertia 13.3 kg·m2 is rotating freely at 50 rev/min. The potter can stop the wheel in 4.5 s by pressing a wet rag against the rim and exerting a radially inward force of 69 N. Find the effective coefficient of kinetic friction between the wheel and the wet rag.