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Virtual work problem

  1. See the diagram: [​IMG]
    The diagram is an ideal mechanical system of massless beams. The platform C holds a weight of "W". There are gear-motor mechanisms at connections A and B, which provide internal torques.

    Suppose, the smaller (acute) angle between beam OA and horizontal is θ.
    The mechanism at A provides an initernal torque to maintain the smaller angle BAO = 2θ.
    The mechanism at B provides an initernal torque to maintain the smaller angle ABC = 3θ.

    Using principle of virtual work (δU=0), find the minimum moment M which must be applied at O to raise the load W.

    Please help in solving the above problem. I cannot find a way to calculate the virtual work done by W when the virtual work done by M is Mδθ. Also what will happen to the internal torques provided. Will they appear in the moment M expression?

    Thanks for the help.
    Last edited: Oct 16, 2011
  2. jcsd
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