Question

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 athlete’s average velocity for the first half of the
swim?
(b) What is the average velocity of the athlete for the second half
of the swim?
(c) What is the athlete’s average velocity for the round trip?

Answer 1

Average velocity = displacement / time (include direction).

(a) From north to south: displacement = −50.0 m, t = 20.0 s.
v_avg = −50.0 / 20.0 = −2.50 m/s (2.50 m/s toward the south).

(b) Return (south to north): displacement = +50.0 m, t = 22.0 s.
v_avg = +50.0 / 22.0 = +2.27 m/s (2.27 m/s toward the north).

(c) Round trip: net displacement = 0, total time = 42.0 s.
v_avg = 0 / 42.0 = 0.00 m/s.