Question

Okay I got an answer of 9 ft/s but the book says the answer is 837/sqrt(8674)..how did they get this??? A man starts walking north at 4ft/s from a point P. Five minutes later, a woman starts walking south at 5ft/s from a point 500ft due east of P. At what rate are the people moving apart 15 min after the woman starts walking?

Answer 1

It would be 9 ft/sec if they were on the same line but going opposite directions... think about 2 people walking apart on a sidewalk.

But these people are on two separate parallel sidewalks, separated by 500 feet.

So their rate of moving apart depends on the angle that they are at... the angle changes as they walk