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Homework Help: Simple relative motion

  1. Mar 1, 2010 #1
    1. The problem statement, all variables and given/known data

    Two ships, one moving 15 degree west of north with a speed 25 mi/h., the second moving 25 degree south of west with a speed 20 mi/h. relative to water pass each other. Find the velocity of the second ship relative to the first ship (magnitude and direction).

    2. Relevant equations

    V1 + r = V2
    V2 - V1 = r

    3. The attempt at a solution

    I want to confirm on this.

    My approach is using this relation.
    V1 + r = V2
    and so V2 - V1 = r, where r is the velocity we are looking for of our problem.

    Then I will take components, x and y, and find sqrt(x^2+y^2) and direction tan-1 y/x
  2. jcsd
  3. Mar 2, 2010 #2


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    Science Advisor
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    Hi jwxie! :smile:

    (have a square-root: √ and try using the X2 and X2 tags just above the Reply box :wink:)
    Yes, that's exactly right! :smile:

    (btw, I wouldn't use r, I'd stick to the same area of the alphabet, and use v12 or u or w :wink:)
  4. Mar 2, 2010 #3
    Hi, tiny, thank you for your confirmation. My friend had an exam and he doubted about my explanation. Thank you!

    I will make sure I check all the synatx ^^
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