Wheel Ring 3D print model

Wheel made in Catia V5 and rendered in Keyshot Pro 10.

A wheeled vehicle requires much less work to move than simply dragging the same weight. The low resistance to motion is explained by the fact that the frictional work done is no longer at the surface that the vehicle is traversing, but in the bearings. In the simplest and oldest case the bearing is just a round hole through which the axle passes (a plain bearing). Even with a plain bearing, the frictional work is greatly reduced because:

The normal force at the sliding interface is same as with simple dragging.The sliding distance is reduced for a given distance of travel.The coefficient of friction at the interface is usually lower.