Wednesday, September 10, 2014

classical mechanics - Does the conservation of fracpartialLpartialdotqi necessarily require qi to be cyclic?


If a generalized coordinate qi is cyclic, the conjugate momentum pi=L˙qi is conserved.


Is the converse also true? To state more explicitly, if a conjugate momentum pi=L˙qi=C1

is conserved, will qi be necessarily cyclic? If we integrate (1), we get L=C1(qi,˙qi)˙qi+C2(qi)qi
From (2), it is evident that the conservation of pi does not necessarily imply qi is cyclic. qi is cyclic only if C2=0 which is only a special case.


Assuming my little observation is correct what is an example (perhaps a physical one) of such a situation i.e., a conserved pi with a non-cyclic qi? I cannot immediately think of one.





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