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Homework Help: Determine directions for 2 dimensional Force Systems

  1. Sep 1, 2009 #1
    1. The problem statement, all variables and given/known data

    Example 1
    http://img143.imageshack.us/img143/6944/86439707.png [Broken]
    Example 2
    http://img266.imageshack.us/img266/2154/ay2.png [Broken]

    2. Relevant equations


    3. The attempt at a solution

    For a smooth pin, there are 2 unknowns. Fx and Fy
    Why does Ay (Fy) act in the -ve(down) direction, and sometimes in the up direction ^
    I'm quite confused :grumpy:
    Does the question got to do with the directions? I will post the question if needed to
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Sep 1, 2009 #2


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    Science Advisor
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    Gold Member

    The direction is dependent on satisfying the equilibrium equations where the sum of forces and moments about a point must equal zero. You can always assume a direction, and if you get a minus sign for your result, you assumed the wrong direction.
  4. Sep 2, 2009 #3
    thanks alot. .:blushing:
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