Halliday, Resnick & Walker — Motion Along a Straight Line: Problem 91

100 m dash. The running event known as the 100 m dash consists of three stages. In the first, the runner accelerates to the maximum speed, which usually occurs at the 50 m to 70 m mark. That speed is then maintained until the last 10 m, when the runner slows. Consider three parts of the record-setting run by Usain Bolt in the 2008 Olympics: (a) from 10 m to 20 m, elapsed time of 1.02 s, (b) from 50 m to 60 m, elapsed time of 0.82 s, and (c) from 90 m to 100 m, elapsed time of 0.90 s. What was the average velocity for each part?