A cyclist travels along a straight, flat road. At first, the cyclist accelerates from rest. After a while, the cyclist reaches a constant (terminal) velocity. Eventually, the cyclist stops pedalling and the bicycle slows down to a stop. Describe and explain the motion of the cyclist during each of these three stages, referring to the forces acting at each stage.

During the first stage the cyclist pedals, producing a driving force that exceeds the resistive forces of friction and air resistance. The resultant force is therefore in the direction of motion and the cyclist accelerates.

In the second stage the cyclist has reached a constant (terminal) velocity. Here the driving force equals the resistive forces, giving a net force of zero. The cyclist moves at a steady speed.

In the final stage the cyclist stops pedalling, so the driving force becomes zero. The resistive forces alone act, giving a resultant force opposite to the motion. This causes the cyclist to decelerate and eventually come to rest. Throughout the ride work is done against the resistive forces, converting kinetic energy into heat and sound.