Question

A swimmer heads directly across a river, swimming at 1.5 m/s relative to the water. She arrives at a point 30 m downstream from the point directly across the river, which is 87 m wide.


(c) In what direction should the swimmer head so as to arrive at the point directly opposite her starting point?

Answer 1

Did you see Sheenybeany's response?

http://www.jiskha.com/display.cgi?id=1407609411

Answer 2

First crossing:
time to cross = 87/1.5 = 58 seconds
so speed of current = 30/58 = .517 m/s

second crossing
v upstream = 1.5 sin A = .517
sin A = .345
A = 20.2 degrees

then if they ask:
v across = 1.5 cos A