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Homework Help: Free body diagram of a beam construction

  1. Mar 12, 2015 #1
    1. The problem statement, all variables and given/known data
    Beams AC and BD are light (no mass) and they're conjoined at B. Points A and D are fixed but frictionless. The radius of the wheel is R and the weight hanging on the pulley has the mass m.

    2. Relevant equations

    3. The attempt at a solution
    I'm stuck at the very beginning of the problem which is to draw a free body diagram (the body is in equilibrium) of the construction however my equations dont add upp. The obstacle I'm currently facing is knowing which way the all the different forces are facing.

    Attached Files:

  2. jcsd
  3. Mar 12, 2015 #2


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    Staff Emeritus
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    Homework Helper

    You know that the hanging mass m is affected by gravity. Start there and work back into the structure.

    If you need more detailed help, you should post your FBD and the equations you're having trouble with.

    P.S.: I'm moving this thread to the Engineering HW forum, which is a more relevant forum than Advanced Physics.
  4. Mar 12, 2015 #3


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    Science Advisor

    Make free body diagrams of each piece. You know the sum of moments about any point is zero and that all forces add to zero. The trick is to choose convenient points to take moments about.
  5. Mar 13, 2015 #4
    Solved it! Thank you both for the reply.
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