When discussing the motion of an Olympic sprinter for something like the hundred meter dash, one often talks about the maximum speed of the sprinters in the race. However, have you ever wondered what the acceleration is for one of those sprinters, and how long it takes to reach their maximum speed? Approximately two months ago, Usain Bolt, an Olympic runner from Jamaica, set the world record for the 100 meter dash in a time of 9.58 seconds!
To put that in perspective, that’s an average speed of 10.43 m/s. However, we all know that that was not his maximum speed during the race. It has been thought that sprinters typically reach their top speed at around 50-60 meters; Bolt reached his top speed at the distance of 60-80 meters, at which point he was running at the incredible rate of 12.42 m/s (27.79 mph). Assuming that he slowed a little bit in the next twenty meters, we can assume that he ran the final forty meters of the race at a somewhat constant speed of around 12 m/s. Therefore, he took 3.33 seconds on the final forty meters, meaning that it took him 6.25 seconds to accelerate from 0 to approximately 28 mph. By using one of our acceleration equations [A = 2(X final)/(t^2)], we are able to determine that Bolt’s acceleration, assuming that it was constant, was an average of 3.072 m/s/s.
This is pretty incredible to imagine, as his acceleration is somewhat close to that of the 2000 Honda moped’s 0-30 mph acceleration time of 5 seconds. On top of that, Bolt was able to accelerate to around 30 mph in about 41 seconds less than a fully loaded school bus! It will be interesting to see the sprinters of the future, and their ability to sprint at mind-boggling speeds. But for now, Usain Bolt’s time of 9.58 seconds in the 100 meter dash will do!