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Homework Help: Contant of motion question

  1. Dec 18, 2009 #1
    what does it mean for momentum to be constant of motion.
    i know that if it is it will commute with the hamiltonian but what does it mean in words?
  2. jcsd
  3. Dec 18, 2009 #2
    If momentum is a constant of motion, there's a couple of things it means:

    (1) momentum is conserved--the total momentum of the system (at least in the particular direction/angle) is constant
    (2) the time derivative of momentum is zero ([itex]\dot{p}=0[/itex])--this does not mean there is no motion, just that the time-evolution of the motion is non-existent.

    You should look at "[URL [Broken] Theorem[/url] and http://en.wikipedia.org/wiki/Constant_of_motion" [Broken]. These wiki articles might help you understand more.
    Last edited by a moderator: May 4, 2017
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