View source for Jourdain principle

A differential-variational principle in mechanics, established by P. Jourdain [[#References|[1]]], isolating the actual motions of a system in the class of kinematically-possible motions satisfying conditions of ideal constraints imposed on the system and the conditions of constancy of positions of the points in the system for the moment of time under consideration. According to the Jourdain principle, for an actual motion of a system constrained by ideal two-sided (restraining) constraints, the sum of the elements of work done by the active forces and inertial forces for arbitrary variations in the kinematically-possible velocities is zero at every moment of time. See also [[Variational principles of classical mechanics|Variational principles of classical mechanics]].

====References====
<table><TR><TD valign="top">[1]</TD> <TD valign="top">  P.E.B. Jourdain,   "Addition to papers on the equations of mechanics"  ''Quart. J. Pure Appl. Math.'' , '''39'''  (1908)  pp. 241–250</TD></TR></table>



====Comments====
The principle was used before Jourdain in the 18th century already, and only later acquired the name  "Jourdain principle" .