Q1. A proton is initially at rest at a point where the potential is 515V. Sometime later the proton is at a point where the potential is 190V. If no force other than the electrostatic force acts on the proton, what is its final kinetic energy?

Q2. A potter's wheel having a radius 0.45 m and a moment of inertia 10.7 kg•m2 is rotating freely at 50rev/min. The potter can stop the wheel in 5.0 s by pressing a wet rag against the rim and exerting a radially inward force of 75N. Find out the effective coefficient of kinetic friction between wheel and wet rag.