  This work is basically about the general form of Newton's second law for
variable mass problems. We develop a model for describing the motion of the
one-dimensional oscillator with a variable mass within the framework of
classroom physics. We present a simple numerical procedure for the solution of
the equation of motion of the system to be implemented by students and
teachers. Interesting qualitative concepts as well as quantitative results for
the focused problem are presented.
  The topic has pedagogical value both from theoretical and experimental point
of view. However, this article considers only theoretical aspects of the
problem. The work is addressed to basic physics courses at undergraduate level.
