In the wheel vs ski analogy, what concept is illustrated by the more effortless rolling of wheels compared to skis?

In the wheel vs ski analogy, what concept is illustrated by the more effortless rolling of wheels compared to skis?

• A. Rolling friction
• B. Sliding friction
• C. Maintenance of bearings
• D. Bearings friction concept

Answer: (A)

The main idea is the difference between rolling friction and sliding friction. When a wheel rolls, only a small contact patch is touching the surface at any moment and the wheel rotates, so most energy losses come from tiny deformations and the axle’s resistance rather than constant sliding. This rolling friction is usually much smaller, so moving a wheel feels effortless. Skis, on the other hand, slide across the snow, so the entire contact area is moving against the surface and the snow has to be sheared and displaced, which creates more resistance and requires more effort. That’s why wheels roll more easily than skis. Bearings and lubrication can reduce rolling friction further, but the key point is that rolling friction is lower than sliding friction.