 The action allows identification of conserved quantities for mechanical systems, even when the mechanical problem itself cannot be solved fully, because any differentiable symmetry of the action of a physical system has a corresponding conservation law, a theorem due to Emmy Noether.All classical equations of motion can be derived from the variational principle known as Hamilton's principle of least action

stating the path the system takes through the configuration space is the one with the least action .In electrodynamics, the force on a charged particle of charge is the Lorentz force