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Homework Help: Relative Velocity: Riverboat and Canoe

  1. Jan 26, 2016 #1
    1. The problem statement, all variables and given/known data
    A canoe has a velocity of 0.420 m/s southeast relative to the earth. The canoe is on a river that is flowing at 0.550 m/s east relative to the earth.

    This can't be seen in the problem statement, but the angle between the two vectors is 45 degrees. As implied by the question, the southeastern one is off at a tilt; while, the river (the eastern one) is at the origin pointing outward straight, horizontally at 0 degrees.

    Find the magnitude of the velocity vāƒ— c/r of the canoe relative to the river.

    2. Relevant equations
    Vsub(B|A) = Vsub(BC) - Vsub(AC)

    3. The attempt at a solution
    So I thought: Find the magnitude of the tilted vector and then subtract 0.55 from it. This has turned out to be wrong. I did:

    Square Root(0.42*Sin(Pi/4)^2 + 0.42Cos(Pi/4)^2) = |Canoe|
    |Canoe| - 0.55 = 0.612
    Wrong answer
  2. jcsd
  3. Jan 26, 2016 #2
    To add or subtract vectors, it is necessary to compute the x and y components of each vector.

    The x component of the sum is the sum of the x components. etc.
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