physics111
posted by yonela .
a river flows due south with a speed of 2.0m/s. a man steers a motorboat across the river;his velosity is 4.2m/s due east.the river is 800m wide.
(A) what is his velocity(magnitude and direction)relative to the earth?
(B)how much time is required to cross the river?

b. time to go across: distanceEast/VelocityEast
a. he is heading upstream:
direction=arctan2/4.2
magnitude: speed=sqrt(4.2^2+2^2)