Think of a car's tires spinning out on snow covered roads, or a bowling ball sliding down the lane before it starts rolling smoothly. These everyday examples illustrate the difference between rolling with and without slipping.

An object rolling on a surface has two independent motions: translational velocity $v_\text{CM}$ of its center of mass and angular velocity $\omega$. For a radius $R$, we saw previously that the rolling without slipping condition is

When this equality fails, the object is rolling while slipping.

Detecting Slip

Compare $v_\text{CM}$ to $\omega R$ at any instant.

Pure Rolling: $v_\text{CM} = \omega R$

The contact point has zero velocity relative to the surface.

Overspinning: $v_\text{CM} < \omega R$

The wheel spins faster than needed. The contact point slides backward relative to the surface. This occurs when wheels spin on ice.

Underspinning: $v_\text{CM} > \omega R$

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