  In this paper, variational techniques are used to analyze the dynamics of
nonholonomic mechanical systems with impacts. Implicit nonholonomic smooth
Lagrangian and Hamiltonian systems are extended to a nonsmooth context
appropriate for collisions. In particular, we provide a variational formulation
for implicit nonholonomic mechanical systems with collisions, for those
collisions that preserve energy and momentum at the impact. Lastly, the
theoretical results are illustrated by examining the example of a rolling disk
hitting a wall.
