Motion and Its Causes

Force and Newton’s Laws of Motion

Do rolling objects experience contact friction?

Whether it is a bowling ball rolling down the alley or a wheel rolling on the road, there is no sliding between the ball or wheel and the flat surface, so there can be no contact friction. What is the cause of rolling friction? Rolling friction is the result of deformations of either the rolling object or the surface. Think about how much faster a rolling ball stops on grass or sand than on a hard surface. In those cases the ball has to push down the surface in front of it, which acts the same as contact friction. Or, remember when you rode a bicycle with soft tires. In this case the tire is squeezed when it contacts the street, which also acts like friction.


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