
this article has been published in theblogpaper sneak preview

Published on the 25th of September 2009, around 5.000 copies have been printed and distributed throughout London
This week has left biologists and statisticians speechless as Usain Bolt smashed his 100m record by over a 10th of a second (a video I have watched an extortionate amount since Sunday).
His closest competitor, Tyson Gay, ran a 9.71 (pretty close to Bolt's previous record-breaking run in Beijing of 9.69). In short distances like the 100m, a tenth of a second is an age. Technological advances in sports clothing have given us lighter shoes and aerodynamic materials, designed to streamline the body. In a sport where every hundredth of second counts, an athlete's weight is crucial.
So why, in the name of all that is holy, would the elite athletes drag themselves down with the unnecessary jewellery that the 100m finalists were wearing on Sunday?
Here comes the science bit, concentrate...
Lets say that, during his 100m final, Usain Bolt is running at top speed (roughly 12.44 metres per second*) by the time he reaches 60 metres. Bolt reached 60m in 6.31 seconds and he weighs 86kg (it's amazing what you can find out online). That's an acceleration of just under 2 metres per second, per second.
Force = mass x acceleration
172 Newtons.
Add a watch (10g), a bracelet (7g) and a gold chain with a ring around it (15g) and the extra force required to accelerate to top speed is an extra 0.064 Newtons!
OK, in reality that isn’t very much, in fact it’s the equivalent to a slight breeze. But in a sport where a race is cancelled if there's a tail wind blowing at more than 2 m/s then this is a significant difference.
If...
...then check the table below. Usain and Gay (sans jewellery) came first and second.
Bet you wish you'd paid more attention in physics class now eh?
100 Metres Final

* Calculated using the time it takes for him to run between the 60m and 80m marks during his 100m final.
Comments
That just shows how quick Bolt is, the other competitors needed standard time to figure out how long it took for them to finish after Bolt.