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Homework Help: Crossing a river?

  1. Sep 10, 2009 #1
    1. The problem statement, all variables and given/known data

    A hunter wishes to cross a river that is 1.5 km
    wide and that flows with a speed of 6.6 km/h.
    The hunter uses a small powerboat that moves
    at a maximum speed of 14 km/h with respect
    to the water.
    What is the time necessary for crossing if
    the boat goes directly across the river? An-
    swer in units of min.

    2. Relevant equations

    3. The attempt at a solution
    I dont even know where to start.
  2. jcsd
  3. Sep 10, 2009 #2


    User Avatar
    Gold Member

    welcome to PF megamax48 :smile:

    you need to find the net velocity acting on the boat, calculate the angle with respect to the boat speed vector [theta=tan-1 vy/vx=tan-1 vriver/vboat], get the distance using the angle and the river’s width, finally calculate the time using the calculated distance and the net velocity. you better draw this so you can understand it well

    ps. don't forget to convert the units
    Last edited: Sep 11, 2009
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