Euler–Lagrange equations
Stationary action supplies coordinate equations of motion.
Key knowledge
For a smooth Lagrangian L(q,q̇,t), stationary action under fixed-endpoint variations gives d(∂L/∂q̇_i)/dt − ∂L/∂q_i = 0.
Values and equations
d(∂L/∂q̇_i)/dt − ∂L/∂q_i = 0
- L
- Lagrangian J
- q_i
- Independent generalized coordinate, with its own coordinate unit
- q̇_i
- Coordinate rate
- t
- Time s
Conditions and scope
- Use independent generalized coordinates after any holonomic constraints are handled; L and paths must permit the displayed time derivatives and integration by parts.
- This homogeneous form excludes unrepresented nonconservative generalized forces; stationary need not mean minimum.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Sections 1.5–1.5.2: stationary variation and Lagrange equations.
2026-10-10 · First-derivative classical action with stated variations only; higher-derivative and nonholonomic systems excluded.
Entry details
Permanent link to this entry ↗- Record identity
- physics-euler-lagrange-equations
- Revision
- university-reference.1
- Structured reference record
- University reference · University core expansion