Very few people in the world can run 100 meters in less than 10 seconds.

• How can you measure a runner's speed?
• Does running twice as far take twice as much time?

Record your ideas about these questions in your Active Physics log. Be prepared to discuss your responses with your small group and the class.

FOR YOU TO DO

1) Your teacher will indicate the location of the "track." Place a mark on the track at the 0-, 5-, 10-, 15-, and 20-m positions.

2) Place students with stopwatches at the 5-, 10-, 15-, and 20-m marks to serve as timers. Each timer should measure the amount of time for each runner to reach the timer's assigned mark.

3) Have someone serve as starter, saying "Ready, Set, Go!" for each runner. All watches should be started on the "Go" signal, and each watch should be stopped as the runner passes the timer's assigned mark. Measure the time for three runners.