Solving Constants of Motion for Particle in 3D - No Quotes

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[SOLVED] Constants Of Motion

A Particle of mass m moves in three dimensions under the action of a conservative force with potential energy V(r).Using the sperical coordinates r, \theta,\phi, obtain the hamiltonian function for the system.
Show that P_{\phi} , \frac{P^{2}_{r}}{2m} + \frac{P^{2}_{\phi}}{2mr^{2}sin^{2}\theta} + V(r) and P^{2}_{\theta} + \frac{P^{2}_{\phi}}{sin^{2}\theta} are constants of motion.

I found the hamiltonian, H = \frac{P^{2}_{r}}{2m} + \frac{P^{2}_{\theta}}{2mr^{2}} + \frac{P^{2}_{\phi}}{2mr^{2}sin^{2}\theta} + V(r).


Since \phi is cyclic we have P_{\phi}^{'}=0 or P_{\phi} is a constant of motion. I don't have much idea about the rest. Do u people have any suggestions? Thanks in advance..
 
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Hi, abeen,

Welcome to PF.

From the way you phrased your questions, it sounds like you are seeking advice for how to attack a homework problem. If so, there's a special forum at PF for that (look up above for the "sticky"). If not, we can help you right here.
 
abeen said:
. I don't have much idea about the rest. Do u people have any suggestions? Thanks in advance..

Hint: Poisson bracket
 
siddharth said:
Hint: Poisson bracket

Thanks.Can you please give me a brief account of the methods for identifying a constant of motion.
 
abeen said:
Thanks.Can you please give me a brief account of the methods for identifying a constant of motion.

That was the hint. If F(p,q) is a constant of motion and H is the hamiltonian, what can you conclude about {H,F} ?
 
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