An undergraduate study of harmonic and parametric motion of a simple   spring-mass system from motion waveforms
  The spring-mass system studied in undergraduate physics laboratories may show complex dynamics due to the simultaneous action of gravitational, elastic, and torsional forces, in addition to air friction. In this paper, we describe a laboratory exercise that caters to beginning students while giving those with more background an opportunity to explore more complex aspects of the motion. If students are not given predefined apparatus but are allowed to design the experiment setup, they may also learn something about physics thinking and experimental procedure. Using results thus produced, we describe a variety of spring-mass oscillation patterns, discussing the physics of the significant deviations from simple harmonic motion. The parametric oscillation behavior we have observed is reported and investigated. This study is based on analysis of motion waveforms. 
Ilario Boscolo, Fabrizio Castelli and Marco Stellato
physics.ed-ph physics.class-ph