Wolfram Demonstrations Projecthttp://demonstrations.wolfram.com/An Open Resource of Interactive Mathematica VisualizationsCopyright 2009 Wolfram Demonstrations Project & ContributorsOscillations of a Pogo Stickhttp://demonstrations.wolfram.com/OscillationsOfAPogoStick/]]>http://demonstrations.wolfram.com/OscillationsOfAPogoStick/