4 articles
Action (physics)
In physics, the action is a scalar quantity, an integral of the Lagrangian over time along a path, whose stationary value characterizes the actual motion of a system.
D'Alembert's principle
D'Alembert's principle, also called the Lagrange–d'Alembert principle, is a statement in classical mechanics, enunciated by Jean le Rond d'Alembert in 1743, that reduces problems of dynamics to problems of statics.
Lagrangian mechanics
Lagrangian mechanics, or Lagrangian dynamics, is a reformulation of classical mechanics in which equations of motion follow from the Lagrangian and Hamilton's principle of stationary action.
Principle of virtual work
The principle of virtual work states that a mechanical system is in equilibrium only when the total work of applied forces vanishes for every virtual displacement.