Which type of friction occurs between rolling surfaces?

• A. Sliding friction
• B. Fluid friction
• C. Static friction
• D. Rolling friction

Answer: (D)

Rolling friction is the resistive force that appears when something rolls over a surface. It comes from tiny deformations and recoveries at the contact patch as the wheel or cylinder rolls, which dissipate energy as heat and vibrations. This makes rolling friction typically smaller than sliding friction, the resistance you’d feel if surfaces were sliding past each other. Static friction, on the other hand, is what can keep a wheel from slipping and doesn’t by itself account for the energy losses of rolling. Fluid friction involves a surrounding fluid, not a solid–solid contact. So the friction occurring between rolling surfaces is rolling friction.