On nonholonomic systems and variational principles

We consider the compatibility of the equations of motion which follow from d’Alembert’s principle in the case of a general autonomous nonholonomic mechanical system in N dimensions with those equations which follow for the same system by assuming the validity of a specific variational action principle, in which the nonholonomic conditions are implemented by means of the multiplication rule in the calculus of variations. The equations of motion which follow from the principle of d’Alembert are not identical to the equations which follow from the variational action principle. We give a proof that the solutions to the equations of motion which follow from d’Alembert’s principle do not in general satisfy the equations which follow from the action principle with nonholonomic constraints. Thus the principle of d’Alembert and the minimal action principle involving the multiplication rule are not compatible in the case of systems with nonholonomic constraints. For simplicity the proof is given for autonomous systems only, with one general nonholonomic constraint, which is linear in the generalized velocities of the system.