Equation 8-13 says that there is a direct proportionality between the linear speed \(v_\mathrm{CM}\) and angular speed \(\omega\) of a circular object that rolls without slipping. As the wheel in Figure 8-13 rolls downhill it gains speed so \(v_\mathrm{CM}\) increases, and it rotates faster so \(\omega\) increases, but these increases are always proportional to each \perpher so that \(v_\mathrm{CM}\) and \(\omega\) are always related by Equation 8-13.