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Free Body Diagram from Space Diagram

  1. Mar 5, 2012 #1
    1. The problem statement, all variables and given/known data

    http://desmond.imageshack.us/Himg804/scaled.php?server=804&filename=img1.gif&res=medium
    I have to change this space diagram into a free body diagram and i am struggling

    2. Relevant equations



    3. The attempt at a solution

    I have put a reaction force in the the x direction at point J and a rection force in the y direction at point j aswell. I have also done the same at Point E. I don't no if this is right? I'm not sure if there is meant to be a moment force somewhere? Could anyone help?
     
  2. jcsd
  3. Mar 5, 2012 #2

    OldEngr63

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    Gold Member

    The purpose of the wheel at J is to prevent any horizontal reaction at that point, so the only external force there is vertical. Now at E, the pin will support both a horizontal and vertical force, but no moment, so forces in both directions there are correct.
     
  4. Mar 5, 2012 #3
    thanks very much !
     
  5. Mar 5, 2012 #4

    Femme_physics

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    Gold Member

    Are you only asked for a free body diagram?

    Because, it's also important you get the vectors direction right, and this you can normally only do with calculations.

    While in principle pin E supports both a horizontal and a vertical force, you can see that no horizontal force is applied at the structure. So there is no horizontal force there at E.

    Also, you can see that both vertical reactions at J and E will point up, because all the other forces in between them point down.
     
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