[jameshart]

200m split times are routinely tracked - see e.g. https://world-track.org/2022/07/what-are-noah-lyles-splits-f... (it turns out the US national 200m record was broken a couple days ago)

And it is absolutely the case that the times for world class second-100m of a 200m sprint are generally lower than even world record 100m sprints (in that report above, out of the field of 8, 6 runners beat the 100m world record over their second 100m)

Usain Bolt's world record 100m from a stationary start is 9.58s. His world record 200m splits were 9.92s and 9.27s.

Over the middle 100m, his time was 8.84s.

(see https://speedendurance.com/2009/08/21/usain-bolt-200-meter-s...)

So yes, a flying start makes a massive difference. 200m runners are generally slowing down in their second half (Bolt's last 50m took 4.75s, while he covered 100-150m in 4.52s, and 50-100m in 4.32s), but their average speed over the final 100m is still faster than a 100m runner. In a 100m sprint the runner may still be accelerating by the time they reach the line.

[gus_massa]

I just remembered that all (some?) boat races start like this. You must cross the starting line after the initial time, but you can already have speed.

[rcxdude]

Yes, though this is for the practical purpose that having a bunch of sailboats trying to stay completely still is a recipe for chaos.