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Statics: Mechanical Equilibrium

  1. Sep 25, 2005 #1
    I need some help in this problem to see if my game plan is right. My answer doesn't make sense, well to me it doesn't.

    A weight of 200 lb hangs from a frame of negligible weight, as shown. If the frame is in equilibrium, determine the loads acting on the frame at A and D. Use the fact that the frame acts as a three-foce element to check your answer.

    -they are all pin connections
    -theres a 45 45 90 degree triangle there.

    First off i drew a FBD for just DB, and found that it is a two force element, so the line of action passes through the force points of application.

    Then when i draw a FBD for ABC the forces at B, it is just a force pointing at a 45 degree angle. Then theres a force Ay and Ax at A and the 200 lb force acting downward at C.

    the sum of the forces in the x direction

    -Ax -B cos45 = 0

    The sum of the force in the y direction

    Ay + B sin45 - 200 lb = 0

    The sum of the moments in the z direction at point A

    -(6ft)(200lb) + (3ft)(Bsin45) = 0

    Attached Files:

    Last edited: Sep 25, 2005
  2. jcsd
  3. Sep 26, 2005 #2
    ok i think i'm using the idea of a 2-force element wrong.

    The diagram that i have there needs to be zoomed in a bit, doesn't seem to show up right cause some browsers resize it.
    If you need a better diagram then i'll try to scan it this time instead of using paint.
  4. Sep 26, 2005 #3
    Member DB is a two force member, that makes the analysis simple.
  5. Sep 26, 2005 #4
    At A, for the force i get

    0 for the x component
    200 lb for the y component

    anyone else get these values at point A?
  6. Sep 26, 2005 #5
    no, Fax=400lb, Fay= 200N down
  7. Oct 5, 2005 #6

    If anyone ever needs the solution, I'd be more than happy to help you come to it
  8. Oct 12, 2005 #7
    I got it. I was making this problem more harder than it seemed :cry:
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