Carl lewis once set a world record for the 100.0-m run with a time of 9.86 s. if, after reaching the finish line, mr. lewis walked directly back to his starting point in 90.9 s, what is the magnitude of his average velocity for the entire trip?

Explanation: Average velocity is defined as net displacement made per unit time . Displacement is defined as minimum distance between starting and end point of a journey.

                  If a person during his journey comes back to his starting point at the end of his journey ,  as is happening in the given case of Carl Lewis , then displacement will be zero

Here Net displacement = 0 as initial and final point of journey is the same .

Time taken = 9.86 +90.9 = 100.76 s

Average velocity = net displacement / time

Average velocity = 0 / 100.76 = 0