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Homework Help: Flexible Hinges

  1. Jul 31, 2010 #1
    1. The problem statement, all variables and given/known data

    A frame is made from two beams of equal length joined at the top with a flexible hinge that can open to any angle. A mass, m, is hung by a massless rope from the hinge. The angle between the rope and each of the beams is (phi).

    Find an expression for the force of friction acting between each beam and the floor.

    I have drawn two separate Free Body Diagrams (FBD), one for each beam. However, I am not familiar with "flexible hinges," that open to any angle. How should the forces of the hinge holding the beams together be represented in the FBD? Since the hinge is holding the two beams together, should I represent it as a normal force for each beam, or should the force be a resultant of the normal force and the downward force of the hanging weight between the beams?

    Any insight would be greatly appreciated. Thanks.
  2. jcsd
  3. Jul 31, 2010 #2


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    If I understand your problem correctly, you have 2 beams hinged at the top and resting on the floor forming an 'inverted V' shape (^), and the angle between the 2 beams at the vertex is (2 phi) with a mass hung at the hinge. If that's the case, it is a truss frame, and you should take a FBD of the hinged joint, and determine the horizontal and vertical forces in each of the beams, and at the floor.
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