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Simple Statics Question: Truss Structure

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  1. Jan 30, 2015 #1
    1. The problem statement, all variables and given/known data
    fPO1U5I.png


    2. Relevant equations
    ∑M = 0, ∑Fx = 0, ∑FY = 0

    3. The attempt at a solution
    QbIz4Sq.png

    If so,

    p9oacDR.png
    If so, I will be using the method of sections to cut along the red line as indicated in the picture.

    This gives me 3 equations of equilibrium as shown above. However, before solving these equations i first need to check whether my equations/diagrams are contain all the forces necessary.

    I know that there is a support reaction in the Y direction of magnitude W at point A.
    However, where do I put the support reaction in the x direction? From what I understand there needs to be a support reaction in the X direction as there is a moment generated from the W down and the W up.
     
  2. jcsd
  3. Jan 31, 2015 #2

    PhanthomJay

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    Science Advisor
    Homework Helper
    Gold Member

    If you assume that ED is a zero force member, the truss will be unstable because it will only have one pinned support at A, and rotate clockwise toward the ground, taking the engine along with it. So this is an incorrect assumption. Instead, consider ED as a '2 force' member anchored at E.
     
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