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Homework Help: Hydrostatics Problem

  1. Nov 27, 2003 #1

    I'm currently trying to solve a problem involving hydrostatics, but I'm getting stuck when it comes to drawing the forces in the FBD.

    The original problem is here:

    Diagram & Problem Info

    This is my attempt at drawing the FBD:

    My FBD

    My calculations:

    R(water) = 187.3 kN
    R(mud) = 644.7 kN

    I think that should be correct.

    However, once I isolated the joint at the intersection of A,B, and C, there is no way I can get the joint to be in equilibrium. (See the bottom right corner of my FBD).

    The same problem occurs at D, where the compression force in member D only goes up vertically, but I also have a horizontal component to the reaction force at D.

    What am I doing wrong? Does anyone have any hints/suggestions on how to solve this?

    Thanks a lot!
  2. jcsd
  3. Nov 27, 2003 #2


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    Science Advisor

    You will need to assume that A and D are set in at their base (not hinged) so that they can support sideways forces.
  4. Nov 27, 2003 #3
    Okay, so would the FBDs look something like this, then?

    Second Attempt at FBD
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