  A five-dimensional cosmological model including a single perfect fluid is
studied in the framework of dynamical system analysis. All the critical points
of the system with their stability properties are listed and some
representative phase diagrams are explicitly shown. It is found that the
stabilization of the extra dimension is possible and the observed flatness of
the three-dimensional space is provided for certain ranges of the equation of
state parameter of the fluid during the evolution of the universe. The model
suggested here can be considered as a simplified model for examining the
possible effects of the extra dimensions in the early universe.
