Topic:Advanced Classical Mechanics/Hamilton's Equations
Hamilton's Equations 
Hamilton's equations are an alternative to the Euler-Lagrange equations to find the equations of motion of a system. They are applied to the Hamiltonian function of the system. Hamilton's equations are
Where H is the Hamiltonian, are the generalized coordinates, are the generalized momenta, and a dot represents the total time derivative.
The Hamiltonian can be found by performing a Legendre transformation on the Lagrangian of the system:
where the Einstein summation notation is used, a dot represents the total time derivative, qi are the generalized coordinates, pi are the generalized momenta.
These momenta are found by differentiating the Lagrangian with respect to the generalized velocities . Mathematically
In some cases, H = T + V, the total energy of the system. There are two conditions for this. First, the equations defining the generalized coordinates q don't depend on time explicitly. Second, the forces involved in the system are derivable from a scalar potential. The forces must be conservative (such as gravity).
- Goldstein, Poole, Safko. Classical Mechanics 3rd ed. 2002