The applet on Page 2 simulates the motion of a planet around the sun (or another fixed star), or the motion of a moon or satellite around a planet.

For detailed information on how to use the applet, go to Applet Help on the applet's Help menu and look at Help and ShowMe. A Lesson accompanying the applet is available there as well.

The applet is available in two versions: "Planet Motion 1" and "Planet Motion 2". The applet on Page 2, "Planet Motion 1", allows you to vary the shape of the planet's orbit by varying the eccentricity and semi-major axis of the orbit.

"Planet Motion 2", which is at Kinematics/Acceleration/Due to Gravity/Simulate It/Planet Motion/Planet Motion 2, lets you vary the shape of the orbit by varying the orbit's energy and angular momentum.

The orbit is defined either by the eccentricity and semi-major axis or by the energy and angular momentum. In either version of the applet, the values of the pair of variables not set by the sliders are displayed in the data box.