Instructions: Drag the sliders to set the initial angle and speed of the pendulum. Then press start to watch the animation and see the corresponding motion on the plot, which shows the angular speed on the vertical axis and the angle on the horizontal axis. Press reset to stop the animation and pick new initial conditions.

The motion on the graph always follows a curve of constant energy because the energy of the pendulum is conserved. These are the curves drawn on the right. There are two qualitatively different kinds of curves: the closed loops and the open wavy lines. What’s the physical difference between them?

See also:

• Pendulum with angle versus time graph

• Pendulum with potential energy

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