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Homework Help: Vector addition of forces

  1. Sep 26, 2010 #1

    Suy

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    1. The problem statement, all variables and given/known data
    Three cables pull on the pipe such that they create a resultant force having magnitude FR. If two
    of the cables are subjected to known forces, as shown in the figure, determine the direction θ of
    the third cable so that the magnitude of force F in this cable is a minimum. All forces lie in the
    x–y plane.What is the magnitude of F? Hint: First find the resultant of the two known forces.
    Prob._2-31.jpg
    2. Relevant equations



    3. The attempt at a solution
    I have the solution
    but i don't understand "minimum" in this question?
    "the third cable so that the magnitude of force F in this cable is a minimum. "
     
  2. jcsd
  3. Sep 26, 2010 #2

    JJBladester

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    Gold Member

    [tex]F_{R}=\left[1200sin45\textdegree+800cos30\textdegree\right]\hat{i}+\left[1200cos45\textdegree-800sin30\textdegree\right]\hat{j}[/tex]

    [tex]F_{R}=1541.35\hat{i}+448.53\hat{j}[/tex]

    [tex]\left|F_{R}\right|=1605.28[/tex]

    [tex]tan^{-1}\left (\frac{448.53}{1541.35}\right)=16.22\textdegree[/tex]

    Cheers!
     
  4. Feb 26, 2012 #3
    wat is the solution...can u give me?
     
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