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2D vectors

  1. Sep 17, 2008 #1
    1. The problem statement, all variables and given/known data
    A river flows due North at 3.17 m/s. A boat
    crosses the river from the West shore to the
    East shore by maintaining a constant velocity
    of 8.5 m/s due East relative to the water.
    If the river is 163 m wide, how far downstream
    is the boat when it reaches the East shore?
    Answer in units of m




    The attempt at a solution
    I found the magnitude of velocity which was 9.7187 and its direction.
    I used the law of motion
    y)163=3.17sin(90)t+4.9t^2
    to solve for x) x=8.5cos(0)(time i got for y)+4.9(time i got for y^2)
    Am I going about this the right way?
     
  2. jcsd
  3. Sep 17, 2008 #2

    tiny-tim

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    Science Advisor
    Homework Helper

    Hi blayman5! :smile:
    hmm … I make it 9.07187.
    Nooo … that looks like an accelerated motion equation. :confused:

    i] This is uniform motion

    ii] You don't need to find the time …

    you know the direction from the first part … so just use geometry! :smile:
     
  4. Sep 17, 2008 #3
    So use the magnitude of velocity and direction along with the water velocity and solve for the x side?
     
  5. Sep 17, 2008 #4
    i get it

    tanx=length/width
    width*tanX=length

    163*tan(20.4526)=60.7896
    thanks
     
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