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Statics Question Moment for a Truss

  1. Oct 12, 2013 #1
    1. The problem statement, all variables and given/known data

    I need to find the moment about G. Please ignore the question in the image.

    http://img13.imageshack.us/img13/6086/4cv0.jpg [Broken]

    Uploaded with ImageShack.us

    2. Relevant equations

    r X F
    3. The attempt at a solution

    Moment about G = -(30*800) + (-300*50) + 60 A + 17.32*500 + (-17.32*500(4/5)) =0

    I keep getting A= 621 N but my solution is saying 721N. I am doing something wrong, not sure what.
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Oct 12, 2013 #2


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    You need to look at the moment produced by both components for the 500 lb load at point I.

    The reaction at A should be in lbs rather than newtons.
  4. Oct 12, 2013 #3
    Moment about G = -(30*800) + (-300*50) + 60 A + 17.32*500 + (-17.32*500(4/5)) + (-40*500(3/5)) =0

    When I do that I get 821lb? I am still off....
  5. Oct 12, 2013 #4
    wrong way its 20 thank you!!
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