Use your knowledge of acceleration, average speed, and running starts to explain why it happens?

Question

A common track event is the 4x100m relay, where each athlete each run 100m and passes a baton to the next runner who then runs 100m, and so on until all four runners have gone. The runners receiving the baton can start moving before they receive the baton (i.e., they can begin a running start as along as it is before the starting line). The must have the baton in their hand when they begin 100m run. The average speed of the 400m relay is less than the average speed for the 100m sprint. In the 100m sprint, the runner begins from a stopped position in starting blocks. Use your knowledge of acceleration, average speed, and running starts to explain why it happens.

 

Show Work if needed (Acceleration or Average Speed)

Answer 1

To run 100 m from rest an athlete must first accelerate from rest to her top speed.  The average speed during this time is less than her top speed.  In fact, if her acceleration is constant for this period is half of her top speed.  This makes her average speed for the entire 100 m less than her top speed.

 

If she runs in a relay she can accelerate to her top speed before she is passed the baton.  Assuming, as before, that she can keep running at her top speed for 100 m, then her average speed will be equal to her top speed.

 

In brief: it takes some time to accelerate to the final speed: this lowers the average speed a bit for the entire 100 m.