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Virtual displacement

  1. Feb 9, 2004 #1
    hey, all

    i'm now studiynd analytical mechanics and the subject is Langrange equations. What i can't grasp is the meaning of virtual displacement term.

    The formal definition says that:
    it's a small displacement of particle with agreement to constraints in such a way that no time passes and uknown forces don't change. The displacement itself has no relation to actual particle path.

    there are two places where i get confused:

    1) the definition itself when it says that "no time passes"

    2) the actual calculation of virtual displacement where i don't understand the reason why the differentiation is done only with respect to generalized coordinates (q) and time is ignored...

    Xj - cartezian coordinates
    delta(Xj) - virtual displacement of Xj
    Qk - generalized coordinates

    Last edited: Feb 9, 2004
  2. jcsd
  3. Feb 10, 2004 #2


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