  Non-linear dynamics is not a usually covered topic in undergraduate physics
courses. However, its importance within classical mechanics and the general
theory of dynamical systems is unquestionable. In this work we show that this
subject can be included in the schedule of an introductory classical mechanics
course without the need to develop a robust theory of chaotic dynamics. To do
this, we take as examples conservative non-linear oscillators subject to
time-dependent periodic forces. By introducing the concept of stroboscopic maps
we show that it is possible to visualize the appearance of chaos in these
systems. We also address the example of the forced simple pendulum applying the
same treatment. Finally, we briefly comment on the more general theory of chaos
in conservative Hamiltonian systems.
