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ScienceShot: The Physics of Usain Bolt

25 July 2013 7:15 pm
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Markus Schreiber

In the summer of 2009, during the World Championships in Athletics in Berlin, Jamaican sprinter Usain Bolt set a world record time of 9.58 seconds for the 100-meter dash—but he did so with a slight wind at his back. Now, a new analysis suggests that Bolt’s time without the tailwind would still have been a record-setter. Researchers used weather conditions during the race to estimate Bolt’s coefficient of drag, which is related to his body’s wind resistance. That parameter, along with data about the sprinter’s position (collected by lasers every 0.1 second during the race), suggests that Bolt’s time sans wind assistance would have been 9.68 seconds, the researchers report today in the European Journal of Physics. That’s 0.1 seconds slower than the official result but still good enough to squeak past Bolt’s previous world record time of 9.69 seconds, which he had set at the Beijing Olympics the year before. Race data also show that Bolt sprang from the starting blocks with an acceleration of 9.5 meters per second squared—that’s almost 0.97 g, the acceleration due to Earth’s gravity—and was churning out a whopping 2.6 kilowatts of power (3.5 horsepower) less than 1 second later.

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