What is rolling friction?

• A. The gripping or pulling between two surfaces.
• B. Friction that occurs when two surfaces slide past one another.
• C. Friction under high speed.
• D. Friction of air resistance.

Answer: (A)

Rolling friction is the resistance that opposes the motion of a wheel or other object as it rolls across a surface. It mainly comes from the slight deformation of both the rolling body and the surface at the contact area and the internal energy losses (hysteresis) as those materials deform and recover during each rotation. Because the contact is largely rolling rather than sliding, rolling friction is typically much smaller than sliding friction, which is why wheels make it easier to move heavy objects.

The idea described as gripping or pulling between two surfaces refers to static friction or interlocking that prevents motion, not the resistance encountered while rolling. Friction that occurs when surfaces slide past one another describes sliding (kinetic) friction, not rolling friction. The other options don’t capture the rolling interaction, and air resistance is a separate dynamic force, not friction at the contact surface.