  The main topic of this work concerns the formulation of the equations of
motion and the consequent energy balance that they imply for this type of
systems,
  In particular, the analytical development that we will carry out on the
equations of motion has as its objective the energy balance of the system. the
delicate question of defining the displacements admitted by the system leads,
as we shall see, to a non-univocal definition of the energy of the system,
which finds coherence and unity for a particular class of nonholonomic
constraints.
