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Homework Help: Rowboat crosses a river

  1. Sep 21, 2010 #1
    A rowboat crosses a river with a velocity of 3.30 mi/h at an angle of 62.5 degrees north of west relative to the water. The river is 0.505 mi wide and carries an eastward current of 1.25 mi/h. How far upstream is the boat when it reaches the opposite shore?

    Drew a staight line down in quadrant two and made a right triangle. Then: tan(62.5°) multiplied by 1.25 mi/h = 2.40 mi/h.
    Then figure the time out by distance of 0.505 mi divided by 2.40 mi/h = .210 h.
    Then figure upstream at the opposite shore by: (0.505 mi) x (.210 h) = .106 mi = 560.0 feet.

    I'm confused because I have a vector pointing east and one pointing north at 62.5° north of west and I feel like I'm ignoring the east pointing vector and that I need to do something else. I don't understand WHY though.
  2. jcsd
  3. Sep 21, 2010 #2
    This is wrong. How can the current alone be causing you to travel faster than the speed of the current itself?
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