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Homework Help: How to find constants of motion from this hamiltonian?

  1. Oct 8, 2012 #1
    Given H=p^2/2 - 1/(2q^2)
    How to show that there is a constant of motion for this one dimensional system D=pq/2 - Ht ?

    I tried doing it in my usual way i.e. p'=-∂H/∂q and q'=∂H/∂p and then finding the constants of motion but that doesn't match with what I have to show.

    Please guide me as to how to proceed?
  2. jcsd
  3. Oct 8, 2012 #2
    You can definitely use Hamilton's equations to show that D is a constant of motion. Are you sure you did calculate [itex]\dot{D}=\frac{d D}{dt}[/itex] correctly?
  4. Oct 8, 2012 #3


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    You need to show your work so we can see where the problem might lie.
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