A geometric formulation of Classical Analytical Mechanics, especially
suited to the study of non-holonomic systems is proposed. The argument
involves a preliminary study of the geometry of the space of kinetic
states of the system, followed by a revisitation of Chetaev's definiti
on of virtual work, viewed here as a cornerstone for the implementatio
n of the principle of determinism. Applications to ideal non-holonomic
systems (equivalence between d'Alembert's and Gauss' principles, equa
tions of motion) are explicitely worked out.