The Relay Race Baton Drop
A school athletics squad is preparing for a 4×100 m relay. In a practice run, Runner A hands the baton to Runner B inside the 20 m exchange zone, but the handover occurs only 2 m before the end of the zone. Runner B is already moving at 8 m/s while Runner A is still running at 9 m/s at the moment of handover. The coach notices that during the handover, Runner A continues sprinting rather than decelerating. The team finishes the race in 44.0 s. The coach wants to know whether the handover technique affected the result and what adjustment should be made.
1. Analyse the handover using the concept of relative velocity and explain why the timing of the handover within the exchange zone matters.
Read the worked answer
Relative velocity of the baton with respect to Runner B at handover = 9 − 8 = 1 m/s. Since Runner A is faster, the baton is still moving forward relative to B, so B must reach forward and then accelerate to match A's speed. Because the handover happens only 2 m before the end of the zone, B has very little time to complete the exchange before leaving the zone. If A continues sprinting, the baton may be passed too late, risking disqualification if the exchange is completed outside the zone. The ideal is for A to reach top speed and for B to accelerate so that both are at similar speeds at the moment of handover, allowing a smooth exchange with minimal loss of speed.
2. Calculate the average speed of the team and suggest one concrete change to improve the handover.
Read the worked answer
Average speed = total distance / total time = 400 m / 44.0 s ≈ 9.09 m/s. This is below the typical top speed of a sprinter, indicating a loss during exchanges. One concrete change: have Runner A maintain speed while Runner B accelerates earlier, so that the handover occurs with both runners at similar speeds and earlier in the zone. This reduces the relative velocity at handover and allows B to reach top speed sooner after receiving the baton.