1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Lagrangians and P-Conservation

  1. Oct 19, 2006 #1
    I have a problem with a particle experiencing a central force towards some origin, as well as a gravitational force downwards. I've calculated the Lagrangian, and the equations of motion. Now I'm being asked to see if the system follows conservation of angular momentum. How do I do this? I know it has something to do with seeing if the system is invariant of rotation, but how do I check for that?
  2. jcsd
  3. Oct 19, 2006 #2
    If [tex]\frac{\partial L}{\partial q} =0[/tex] then the conjugate momentum [tex]\frac{\partial L}{\partial \dot{q}}[/tex] is a conserved quantity.

    If that doesn't clear things up, then post what you have for the Lagrangian.
  4. Oct 20, 2006 #3
    But the conjugate momentum is the same as the angular momentum only in some cases.
    Compute H and chech if H commutes with J.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?