  We present an experimental study of the time of flight properties of a gas of
ultra-cold fermions in the BEC-BCS crossover. Since interactions can be tuned
by changing the value of the magnetic field, we are able to probe both non
interacting and strongly interacting behaviors. These measurements allow us to
characterize the momentum distribution of the system as well as its equation of
state. We also demonstrate the breakdown of superfluid hydrodynamics in the
weakly attractive region of the phase diagram, probably caused by pair breaking
taking place during the expansion.
