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I Virtual Displacements

  1. Sep 3, 2016 #1
    Studying Lagrangian mechanics starting from D'Alembert's principle.
    I just ran into this.

    Why virtual displacement doesn't contain time t for it's coordinates
    What does that mean 'take place at a fixed time'?
  2. jcsd
  3. Sep 3, 2016 #2
    The simplest answer is that its not 'real' displacement therefore it must not contain change in time - and thats why its called 'virtual'

    if a geometrical change in the configuration of the physical system is done consistent with the constraints operating on the system then one can formulate a principle which helps in weaning away the force of constrains from equation of motion. and that has certain advantage over newtonian description.
  4. Sep 4, 2016 #3
    Thank you much for fine answer, helped me a lot. Guess need some time to grasp that notion well.
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