FIGURE 12.22 shows the forces acting on the crankset of a bicycle. The crankset is free to rotate about the axle, but the axle prevents it from having any translational motion relative to the bike frame. It does so by exerting force $\vec{F}{}_{\text{axle}}$ on the crankset to balance the other forces and keep $\vec{F}{}_{\text{net}}=\vec{0}$.

FIGURE 12.22 The forces exert a net torque about the pivot point.

Forces ${\vec{F}}_1\text{,}{\vec{F}}_2\text{,}{\vec{F}}_3\text{,}\text{.}\text{.}$. exert torques ${\tau }_1\text{,}{\tau }_2\text{,}{\tau }_3\text{,}\text{.}\text{.}$. on the crankset, but $\vec{F}{}_{\text{axle}}$ does not exert a torque because it is applied at the pivot point and has zero moment arm. Thus the net torque about the axle is the sum of the torques due to the applied forces: