Help me with this one..Thanks?

Question

I posted earlier, but I'm stuck on this one ......I'm having trouble with velocity and how to find the displacement. I know the formula, but I dont know how to find it within the questions. Help me out with this question, give me the formula, and plug in the numbers to get the answer. Thanks

1. An athlete swims from the north end to the south end of a 50.0 m pool in 20.0 s and makes the return trip to the starting position in 22.0 s. a.)What is the average velocity for the 1st half on the swim. b.) Average velocity for the 2nd half of the swim. c.) Average velocity for the roundtrip?

Answer 1

Average velocity = total displacement/ total time
Lets say traveling in a northerly direction is positive velocity. That's your reference system. In part c.) he ends up in the same place he started out so displacement is zero.
a.) v = D /t = -50.0/20.0 = -2.5m/s
b.) v = D/t = 50.0/ 22.0 = 2.273m/s
c.) v = D/t = 0.0/42.0 = 0.0m/s