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Homework Help: Parallelagram of forces

  1. Mar 12, 2009 #1
    Can someone show me how to calculate the resultant forces shown as RF N and R F 1on the attachment please, in simple terms.

    2.I need to work out the following..."Three forces applying to one point,find the resultant force" (magnitude and direction to horizontal line) R F1 and R F N

    3.Any help greatly appreciated.


    Attached Files:

  2. jcsd
  3. Mar 12, 2009 #2


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    Homework Helper

    Welcome to PF.

    The approach that works best for me is the component approach.

    What you have is a vector addition in x,y

    So try taking each Force vector as

    Fv1 = fx1 i + fy1 j
    Fv2 = fx2 i + fy2 j
    Fv3 = fx3 i + fy3 j

    Then just add the i's and the j's and you have your resultant

    F = (fx1+fx2+fx3) i + (fy1+fy2+fy3) j
  4. Mar 12, 2009 #3
    Dont really follow that.This is the first time i have seen a parallelogram of forces.Can you explain how I would find the resultant force in N for RF 1 and RF N on the diagram.

    Many Thanks....Mark
  5. Mar 12, 2009 #4


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    Homework Helper

    Welcome to PF!

    Hi Mark! Welcome to PF! :smile:

    Forces are vectors, so they obey the law of vector addition …

    that means that to add two vectors, you slide one so that it starts where the other one ends

    in other words, you make a vector triangle …

    but it comes out the same if you start both of them from the same point, and make a parallelogram (as in your diagram) …

    to convince yourself that they're the same, just try sliding one of the sides of the parallelogram along to the opposite side :wink:
  6. Mar 17, 2009 #5
    Thanks to all who replied,problem solved!

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