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Virtual displacement

  1. Aug 21, 2014 #1
    While deriving lagrangian equation using D'Alembert's principle, in Goldstien, they defined a variable called "virtual displacement". Why do we need a concept called virtual displacement? What is its signigicance in classical physics?
  2. jcsd
  3. Aug 24, 2014 #2

    You can read in wikipedia about it:


    I am not an expert on this matter but from what I have seen, virtual displacements are small spatial displacements [itex]r_{i}[/itex] (with no time displacement) over the path of motion and are used in Lagrangian mechanics.

    The least action principle is part of Lagrangian mechanics and states that particles follow a path whose action is stationary, which means that any "small" virtual displacements does not change the action.

    You can also read about the least action principle in wikipedia:


    Best regards,
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