Dynamics
EL with Momentum The generalized momentum was defined from the Lagrangian. Euler-Lagrange equations can be written in terms of p. No dissipative forcesNo dissipative forces The Hamiltonian can also be expressed with generalized momentum.
A curve f(x) can be defined in terms of its derivatives. Slope and intercept of tangent Find a new function g in terms of new variable z. Function at maximum Change of Variable
Legendre Transformation The Legendre transform replaces one variable with another based on the derivative. Transform is own inverse Partial derivatives for multiple variables Thermodynamics uses the transform for energy. Enthalpy H Internal energy U
Hamiltonian Variables The Legendre transformation links the Hamiltonian to the Lagrangian. Independent variables q, pIndependent variables q, p Velocity a dependent variableVelocity a dependent variable The Hamiltonian should be written in terms of its independent variables Replace velocity with momentumReplace velocity with momentum
Incremental Change An incremental change in the Lagrangian can be expanded Express as an incremental change in H. Independent of generalized velocity changes
Canonical Equations The Hamiltonian can be directly expanded. Each differential term matchesEach differential term matches These are Hamilton’s canonical equations. Lagrangian system: f equationsLagrangian system: f equations Hamiltonian system: 2f +1 equationsHamiltonian system: 2f +1 equations next