This page enables you to experiment with spring-and-mass systems.
The two graphs above show the usual model for a spring-and-mass system. This model tracks two key variables -- the position of the mass and its velocity. The graph on the left (with a blue background) shows the phase plane. The graph on the right (with a green background) shows the position and velocity as functions of time. The initial values are indicated by a red square on the phase plane and along the vertical axis on the right graph. You can change the initial values of the position and velocity by clicking on the phase plane. You can also change the initial position by clicking on the left and right arrows above the phase plane and you can also change the initial velocity by clicking on the up and down arrows to the right of the phase plane.
You can focus on a particular time by clicking on the right graph (with a green background). The time you have chosen is indicated by a vertical line on this graph and by a black dot on the phase plane.