500
Read carefully! At the start of his race, Usain Bolt is running fast enough to travel 20 meters in 4 seconds. At the end of his race, 5 seconds later, he is running fast enough to travel 80 meters in 4 seconds. What is his acceleration?
3 m/s^2
Acceleration = (final speed - start speed)/time
Final speed = 80 meters/4 seconds = 20 m/s
Start speed = 20 meters/4 seconds = 5 m/s
Acceleration = (20 - 5)/5 = 15/5 = 3 m/s^2