Read the ellipse
Locate the central mass at a focus and compare near and far parts of the orbit.
AP Physics 1 · Unit 6 · Energy and Momentum of Rotating Systems
Elliptical Orbits and Gravitational Energy
Trace an elliptical orbit, compare equal-time swept areas, and explain changing orbital speed with gravitational potential and kinetic energy. Finish with a five-question conceptual review.
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Learn by doing
Three ideas you’ll put into motion
Compare equal times
Observe swept areas to connect an orbit’s geometry with changing speed.
Use energy evidence
Track kinetic and gravitational potential energy, then explore the escape condition.
The big idea
The key ideas, at a glance.
Speed changes around an ellipse
For an ideal bound orbit, the satellite moves faster near the central mass and slower farther away. Equal-time intervals sweep equal areas.
Gravity exchanges energy
With zero potential at infinity, U = −GMm/r. In an isolated ideal orbit, kinetic and potential energy change while their sum stays constant.
A quick comparison
Compare the near and far points of the same bound orbit.
Nearer: fasterFarther: slower
Teaching this topic?Classroom fit, AP connections, and support
- Classroom fit
- Use for a concept introduction, guided independent practice, or a projected class discussion.
- Before students begin
- Circular orbits, kinetic energy, gravitational potential energy, and negative values.
- Built-in support
- Prepared scenes, guided prompts, and feedback on lesson questions.
- AP Physics 1 connections
- Unit 6: energy and momentum of rotating systems, applied to orbital motion.
- Check for understanding
- Ask how kinetic and gravitational potential energy change as a satellite moves away from the source.
- Optional extension
- Try the Elliptical Orbit lab.
Ready to test your thinking?
The first scene is set up. Start the lesson and explore.