The simplest angular motion is one in which the body moves along a curved path at a constant angular velocity, as when a runner travels along a circular path or an automobile rounds a curve. The usual problem here is to calculate the centrifugal forces and determine their effect on the motion of the object.A common problem solved in many basic physics texts requires determination of the maximum speed at which an automobile can round a curve without skidding. We will solve this problem because it leads naturally to an analysis of running. Consider a car of weight  moving on a curved level road that has a radius of curvature .

Safe speed on a curved path may be increased by banking the road along the curve. If the road is properly banked, skidding may be prevented without recourse to frictional forces. Figure. 4.1 shows a car rounding a curve banked at an angle . In the absence of friction, the reaction force  acting on the car must be perpendicular to the road surface. The vertical component of this force supports the weight of the car