I just watched the men's 100-m sprint final, and it happened exactly as I thought it would (see my previous post by clicking here). Bolt was in lane 7 with Justin Gatlin to his left in lane 6. To Gatlin's left in lane 5 was Yohan Blake. Bolt's reaction time (0.165 s) was faster than both Gatlin's (0.178 s) and Blake's (0.179 s), but Gatlin had the early lead out of the blocks. The shorter Gatlin at 1.83 m (6' 0") tall had greater acceleration than the taller Bolt, who is 1.95 m (6' 5") tall. By the time the sprinters were approximately halfway home, they were upright and at top speed. Gatlin had the acceleration advantage, as scaling arguments tell us, but Bolt had the top speed advantage. Bolt had enough distance left to ensure that his great top speed would give him the gold.
Usain Bolt broke his own Olympic record with a time of 9.63 s, which is 0.05 s slower than his world-record time. The 1.80-m (5' 11") tall Blake was able to pass Gatlin at the end for the silver medal with a time of 9.75 s. Gatlin's bronze-medal time was 9.79 s, just 0.01 s ahead of fellow Americans Tyson Gay and Ryan Bailey.
Scaling laws are powerfully simple approaches to understanding certain aspects of nature. The acceleration advantage Blake and Gatlin had with shorter legs got them off to a quick start, but the long legs of Bolt helped give him the top speed that ultimately prevailed. A complete understanding of the race is more complicated, of course, but it's great to see the predictive power of (relatively) simple physics.
Lightning Bolt made sure that Jamaica would sweep the men's and women's 100-m sprints!
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