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Dynamics
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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.
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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
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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
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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
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Incremental Change An incremental change in the Lagrangian can be expanded Express as an incremental change in H. Independent of generalized velocity changes
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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
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