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Equilibrium equation for a frame

  1. Nov 27, 2013 #1
    1. The problem statement, all variables and given/known data

    http://postimg.org/image/scm11r483/




    So when considering the free body diagram for member BE, why is the force P not included?

    Does the Ex account for the bit of the P=210 that would act on member BE?
     
  2. jcsd
  3. Nov 27, 2013 #2
    The problem statement seems to imply that the force is acting on the pin. The pin is then assumed to exert a force Ex on member BE. In the problem solution, moments are taken about the pin, so the force at E doesn't matter in this moment balance. However, the solution implicitly assumes that the moment at the pin is zero (i.e., BE rotates freely at the pin).
     
  4. Nov 27, 2013 #3

    PhanthomJay

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    Did you solve for Ex? It's quite a bit of P.
    In the FBD of the member, the internal cut is made an infinitesimal distance away from the joint, so it does not include P in your FBD of the member, just internal forces Ex, Ey, CD, and the external roller vertical reaction.
     
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