## Thursday, October 3, 2013

### The Physics Behind The World's Fastest Man

As I was checking out the recent sports news, I saw an article about the world's fastest man, Usain Bolt of Jamaica, and his contract extension with Puma. I knew that he was incredibly fast, but I wondered what made Puma finally make this deal with him. Upon looking up the time it took for Bolt to achieve his World Record the 100 m World Championships in Berlin, I found that it only took him 9.58 seconds to complete the race. I wanted to see how fast Bolt was running at different points during the race.

I plugged these values in to the equation, vavg = (xf – xo)/t, and found that Bolt’s average speed was 10.4 m/s. Although this value is very large, it is simply his average speed for the entire race. I looked up values of his time at different distances to determine his average speeds for each section of the race. From 0-20 meters, his average speed was 6.92 m/s. From 20-40 meters, his average speed was 11.4 m/s. From 40-60 meters, his average speed was 12.0 m/s. From 60-80 meters, his average speed was 12.4 m/s. From 80-100 meters, his average speed was 12.0 m/s. It is interesting to see that he is accelerating until he is at least 80 meters into the race, and that he only slightly slows down at the finish of the race.

After finding out how fast Usain Bolt ran during his World Record race, I was curious about how much work he did during the race. I found his average acceleration during the race to be about 3.00 m/s from an online source. I also found his mass to be about 95 kg. I used the equation F = ma to determine the force that he exerted during the race. This force came out to be 285 N. Using this force, the distance of the race, and the equation, W = Fd, I determined Bolt’s work to be 28500 J. That's a lot of work for only 9.77 seconds.