Paper 1, Section I, B

Classical Dynamics | Part II, 2013

Consider an nn-dimensional dynamical system with generalized coordinates and momenta (qi,pi),i=1,2,,n\left(q_{i}, p_{i}\right), i=1,2, \ldots, n.

(a) Define the Poisson bracket {f,g}\{f, g\} of two functions f(qi,pi,t)f\left(q_{i}, p_{i}, t\right) and g(qi,pi,t)g\left(q_{i}, p_{i}, t\right).

(b) Assuming Hamilton's equations of motion, prove that if a function G(qi,pi)G\left(q_{i}, p_{i}\right) Poisson commutes with the Hamiltonian, that is {G,H}=0\{G, H\}=0, then GG is a constant of the motion.

(c) Assume that qjq_{j} is an ignorable coordinate, that is the Hamiltonian does not depend on it explicitly. Using the formalism of Poisson brackets prove that the conjugate momentum pjp_{j} is conserved.

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