Aswimmer travels from the south end to the north end of a 30.0 m pool in 15.0 s and makes the return trip to the starting position in 19.0 s. what is the average velocity for the roundtrip?

Zero

Explanation:

Average velocity is given by:

where

d is the displacement of the trip

t is the time it takes for the trip to complete

In this problem, the net displacement of the swimmer is zero. In fact:

- First, he swims 30.0 m in the north direction

- Then, he travels back (-30.0 m) in the south direction, to the starting position

Since the final position is equal to the starting position, the displacement is zero:

d = 0

And therefore, the average velocity is also zero.