Why is sliding friction greater then rolling friction?

Question

Why is sliding friction greater then rolling friction?

Answer 1

When something is rolling the surface of the object isn't actually rubbing against the surface it's rolling on very much at all. The area that comes in contact with the ground just touches down and lifts back up, not much actual contact with the surface is done.

Like this: http://www.physclips.unsw.edu.au/jw/roll...

When sliding the two surfaces have to rub, and slide against each other for the object to move, and this causes friction.

Answer 2

when sliding the whole face is in contact with the surface so more friction

with rolling less surface area making contact so less friction

Answer 3

It is NOT because of the "smaller area of contact" of the rolling surface.  After all, if you "skid" a wheel or a ball against the ground, the contact surface area is the same as when you roll the wheel or ball.

Also,  Note that the formulas for the force of friction show that it is dependent only on the object's WEIGHT, not on the contact surface area.

Wikipedia says the source of rolling friction is "hysteresis," which basically means the ball is continually deforming into a nonspherical shape at the contact surface, and losing energy (converting it to heat) due to this nonelastic deformation.  The loss in energy slows the ball down.

Answer 4

More surface area = more friction. WIth rolling friction, a minimal amount of surface area is in contact with the surface at any given time.