How does rolling friction compare to sliding friction?

Answer 1

Rolling Friction is caused primarily by the interference of small indentations formed as one surface rolls over another. This is the idea behind the frictional forces involved with wheels, cylinders, and spheres. In the ideal case of the wheel, we must first look at the forces acting on the wheel. In pure rolling motion, friction is required to stop, start and change the motion of a wheel.

Static Friction is a force which resists the lateral movement of two objects which are touching each other. A simple example of static friction might be a wooden block sitting on a ramp. Unless sufficient force is exerted, the block will not slide down the ramp, because static friction holds its place and resists sliding. When objects have a high coefficient of friction, it means that a lot of force will be required to break through the force of static friction and create movement, while low coefficient means that less force will need to be exerted.