# Why is WR for 4x100m relay less than 4 times WR for 100m sprint.

1. Aug 14, 2012

### glb_lub

Hello,

The 2012 London Olympics concluded a day or two ago. We saw that a few records were broken in athletics. In particular, the 4x100m men's relay record.

Currently the WR are as follows :-

1) 100m Men's sprint - 9.58 s
2) 200m Men's sprint - 19.19s
3) 4x100m Men's relay - 36.84s

The world's fastest man Usain Bolt features in all the races. Thus in the relay the 4 athletes are either as fast as Bolt(i.e Bolt himself) or slower.
Now if one observes the record time for relay, it is 36.84s , which is less than 4 times the 100m sprint record. Whereas the record time for 200m is more than twice the 100m sprint record.

I think I understand why it is so for 200m sprint (it is relatively easier to sustain high speeds for smaller bursts ) . But I am unable to explain the 4x100m relay case in a succinct way.

Each athlete runs 100m in the 4x100m sprint. But only the first runner has to start at the sound of gun fire. Whereas for the other 3 runners, there is a 20m changeover box,during which the baton changes hands. So I guess, the acceleration time and deceleration time for 1st and 2nd runner overlap partially (similarly for 2nd and 3rd , etc).

2. Aug 14, 2012

### Filip Larsen

Since the total time does not include the acceleration of the 3 last runners (the baton gets a "running start" with those runners, so to speak) it is not surprising that the total time is less than 4 x 100m. Even assuming that runners cannot run at their maximum speed when they pass the baton there will be much time saved. For the 400 m relay to compare to 4 x 100 m the next runner would have to wait in his start block and only start accelerating when the baton is in his hand - then you'd see total times >= 4 x 100 m.

3. Aug 14, 2012

### glb_lub

Thanks. That was nicely put.