13. If a track athlete runs an 800 m race at a constant speed of 2 m/s, how long will it take her to win the race?
Type
A. 6.7 min
your
B. 16 min
C. 26.7 min
D. 400 min

Avery hard rubber ball (m = 0.5 kg) is falling vertically at 4 m/s just before it bounces on the floor. the ball rebounds back at essentially the same speed. if the collision with the floor lasts 0.05 s, what is the average force exerted by the floor on the ball?