Q. An 10m, 210N uniform ladder rests against a smooth wall. The coefficient of static friction between the ladder and the ground is 0.55, and the ladder makes a 50° angle with the ground. How far up the ladder can an 850N person climb before ladder begins to slip?
Q. A stone has a mass of 6 × 10-3 kg and is wedged into the tread of an automobile tire, as the drawing shows. The coefficient of static friction between the stone and each side of the tread channel is 0.90. While the tire surface is rotating at a maximum speed of 13 m/s the stone flies out of the tread. The magnitude FN of the normal force that each side of the tread channel exerts on the stone is 1.8N. Suppose that only static friction supplies the centripetal force, and determine the radius r of the tire.