A. Curves on highways are carefully designed to prevent skidding (or non-uniform circular motion) of the car. On a flat road, the normal force is equal and opposite to the weight of the vehicle and its load, and the frictional force points toward the center of the circle the curve would make if constructed as a full circle. Friction is what is opposing the movement in a straight line, which would cause the car to go off the road. In essence, friction prevents skidding of the vehicle out of the curve and keeps the vehicle moving in a curve

Draw the free body diagram for a car navigating a curve on a flat road. What is the maximum speed with which a 985kg car can round a turn of 82m on a flat road if the coefficient of static friction is 0.60?

B. If the speed limit on a flat curve is 35mph, what is the radius of the curve given that the coefficient of friction is 0.68? What should the speed limit in mph be reduced to when the coefficient of friction decreases to 0.23 because of the ice?

C. Why are highway curves often banked, or at an angle, such that the curve slopes downward toward the invisible center of the highway curve? Think about the free-body diagram and forces.