In this paper some geometrical aspects of constrained mechanics are studied
. A symplectic setting for vakonomic mechanics is given, and the conservati
on of the energy is discussed. This formulation needs constraint forces inv
olving accelerations, A reduction procedure is given for Caplygin vakonomic
systems. Finally, a unified geometrical framework for non-holonomic and va
konomic mechanics is described. (C) 2000 Elsevier Science B.V. All rights r
eserved.