Rolling Friction

The invention of the wheel was pivotal to human civilization precisely because rolling motion involves far less friction than sliding motion. When an object slides on a surface, every point of contact moves relative to the ground continuously, so kinetic friction acts throughout. When a wheel rolls (without slipping), the single point of contact with the ground is, at each instant, momentarily at rest relative to the ground — there is no ongoing relative sliding there, so the (large) kinetic friction does not apply. …