The physics of Usain Bolt’s world record sprint

Telegraph : In Berlin in 2009, Usain Bolt set the world record for the 100-m sprint at 9.58 seconds. To evaluate the physics involved in that feat, Jorge Hernandez Gomez of the National Autonomous University of Mexico and his colleagues used computer modeling to calculate Bolt’s energy and power output. They found that, over the race’s duration, Bolt produced 81.58 kJ of kinetic energy. His maximum power output occurred just 0.89 seconds into the race, and his top speed was 27 mph (43.5 kph). The computer models also revealed that only 8% of Bolt’s mechanical energy was used for movement—the rest was used to overcome drag. Bolt stands 6'5" (195.6 cm) and, according to Gomez, has a much less aerodynamic frame than the average person. Gomez believes that may explain the significance of wind direction in sprints. Whereas the 2009 race in Berlin had a 2 mph tailwind, there was no wind at the 2008 Beijing Olympics, where Bolt achieved his previous best (also the world record) of 9.69 seconds.