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Relative Velocity

  1. Dec 7, 2009 #1
    1. The problem statement, all variables and given/known data

    Relative velocity question. A power boat has cruising speed of 60 km/hr. It is
    taking part in a race around three buoys arranged in an equilateral triangle. The
    second buoy, B, is 5 km due East of the starting/finishing buoy, A. The third
    buoy, C, is to the North of the line joining A and B. There is a current flowing at
    10 km/hr from the south-west. In what direction should the boat be steered on
    each leg of the race and how long will it take the boat to complete one circuit.

    2. Relevant equations

    Vb = Vb/w + Vw

    3. The attempt at a solution
    A to B
    Vw = 5(square root 2)i + 5(square root 2)j
    Vb/w 60Cos(theta)i + 60Sin(theta)j
    Vb = 5(square root 2) + 60Cos(theta)i + 5(square root 2)+ 60Sin(theta)j

    5(square root 2)+ 60Sin(theta)j = o
    Sin(theta) =5(square root 2) / 60
    theta = 6.77

    5(square root 2) + 60Cos(6.77)i =66.65i
    Vb = 66.65i + 0j
    t = 0.075hrs
    t = 270.068s
  2. jcsd
  3. Dec 7, 2009 #2


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    Homework Helper

    Welcome to PF, CloudKel!
    Those answers for AB are correct. I don't see how you can do the rest unless you get more specific information about the location of C.
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