ABSTRACT
Friction arises in all machinery where contacting parts move relative to each other. In many cases, it lowers the efficiency of the machine and causes wear, and steps are taken to reduce friction as much as possible by lubrication. This chapter presents analyses of situations both where friction is necessary and where friction is undesirable. In all cases, the expressions developed apply equally to static and dynamic frictional conditions. When a rope or belt is coiled around a shaft or pulley the tendency for the rope or belt to slip depends substantially on the angle subtended by the arc of contact. Disk friction arises when two circular surfaces are placed in contact and rotate relative to each other. Friction clutches or brakes are usually designed to permit the disengagement of the coupled elements during rotation. A wedge is a device used to produce small adjustments in the position of a body.
