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Finding the value of a moment

  1. Feb 20, 2013 #1
    1. The problem statement, all variables and given/known data
    http://i.imgur.com/Laub8lL.png
    Find the total moment created by force F1 about point A.

    2. Relevant equations
    moment = perpendicular distance x force


    3. The attempt at a solution
    I got my resultant distance to be squrt(20). With this in mind, I plugged into my calculator:
    sqrt(20) x 12 x (insert values listed below)
    (numbers in degrees)
    cos(35)
    sin(35)
    cos(55)
    sin(55)

    and I've had no luck with any of this.

    Please help me
     
  2. jcsd
  3. Feb 20, 2013 #2
    The moment is
    FL sin(θ)
    where θ is the angle between the line connecting point A and the point where F acts on the structure and the line of action of the force
     
  4. Feb 20, 2013 #3
    How do i find theta though?
     
  5. Feb 20, 2013 #4
    See drawing
     

    Attached Files:

  6. Feb 20, 2013 #5

    haruspex

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    Call the point where the right-angled bend is B.
    Drop a perpendicular from B to the line of the force. What's the length of it?
    Drop another from B to a line through A parallel to the force. What's the length of that?
     
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