Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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


    User Avatar
    Homework Helper

    Look at your identical post in www.advancedphysics.org[/URL]
    Last edited by a moderator: Apr 20, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook