You’ll probably have seen footage of “the greatest 100m performance in the history of the event” as Michael Johnson put it. But if not, here’s short description:

In the Olympic final of the 100 metres in Beijing, the Jamaican sprinter Usain Bolt accelerated away from the field and then, with victory assured but with 20 metres still to run, started waving his arms and high-stepping in celebration. When he eventually crossed the line ahead of his rivals, he appeared to be dancing.

Despite easing up up, Bolt broke the world record by 0.03 seconds in a time of 9.69 seconds. But his performance raised the question: how fast could he have run?

Bolt’s coach later said he could have done it in 9.52 seconds. Perhaps.

To settle the question, Hans Kristian Eriksen and colleagues at the University of Oslo decided to apply a little physics.

They used video footage of the race to first work out Bolt’s acceleration profile during the 100 metres and that of the silver medallist Richard Thompson.

Bolt clearly slows down towards the end of the race. So the Norwegian team calculated what Bolt’s time would have been had he matched Thompson’s acceleration in the final 20 metres. The answer is a stunning 9.61 seconds.

But they also say he could have done better. Had Bolt outpaced Thompson’s acceleration by 0.5 m/s^2, as he did in the earlier part of the race, the Norwegians say he could have run 9.55 seconds (plus or minus 0.04 seconds). That makes the coach’s assessment look eminently achievable.

Perhaps he knows something we don’t.

Ref: arxiv.org/abs/0809.0209: Velocity Dispersions in a Cluster of Stars: How Fast Could Usain Bolt Have Run?