The ComPADRE Collections

Projectile and Satellite Orbits

David Pundak, Ort Braude College
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This material is replicated on a number of sites as part of the SERC Pedagogic Service Project


This series of interactive lecture-demonstration questions provides a probe of student understanding of fundamental concepts in gravity. There are two questions about basic concepts in satellite orbits. The final question is about the full satellite orbits and the influence of the initial velocity on the shape of the orbit. A conceptual understanding of the properties of orbit can be generalized to help students analyze a large number of different satellite-orbit types.

Learning Goals

The goal of these activities is to develop a conceptual understanding of gravitational force, satellite orbits, and their dependence on the initial velocity. The activity allows students to reveal the connection between the initial velocity of the satellite and the shape of its orbit. Finally, students could apply this understanding to a related -but not obviously identical- problem like moon or planets orbits.

Context for Use

Educational level: first-year college science or non-science students .
Setting: Active lecture question or workshop activity.
Time required: 15 minutes
Special equipment: computer with projector for instructor
Pre-requisite knowledge: basic mechanics - Newton's laws.

Description and Teaching Materials

The demonstration aspects of these questions will be done virtually with "Physlet," a physics java applet.
Gravity Discussion and Applet Instructions (Microsoft Word 25kB Jul23 07)
Another simulation on Projectile Motion can be found in the PhET collection.

Teaching Notes and Tips

This is a nice activity to introduce Gravity and Kepler's Laws. It could also be used as an interactive demonstration or as an individual activity in the context of a studio class.


A question on moon motion: Students compare the radius and period of the moon's orbit with the radius and period of a satellite near the earth.

References and Resources

Physlets, Physics Applets, are small flexible Java applets designed for science education. You do not need to become a Java expert in order to use Physlets. The links on the right in the Physlet contain: tutorials, download instructions, and example problems to help you use Physlets in your teaching.

Physlet Physics: Interactive Illustrations, Explorations and Problems for Introductory Physics - Wolfgang Christian, Mario Belloni, Davidson College. Publisher: Addison-Wesley. Illustration 12.1 on CD.

Physlets Resource Page