posted by Dan .
A rowboat crosses a river with a velocity of 3.30 mi/h at an angle 62.5° north of west relative to the water. The river is 0.795 mi wide and carries an eastward current of 1.25 mi/h. How far upstream is the boat when it reaches the opposite shore?
Velocity component North (across river)
= 3.3 sin 62.5 = 2.93 mi/h
time to cross = .795/2.93 = .272 hr
Velocity component west (upriver)
= 3.3 cos 62.5 - 1.25
= .274 mi /hr
distance upstream = .274*.272 = .0744 mi
*5280 ft.mi = 393 feet