Orbits & satellites

About this lab: Orbits and satellites

Circular orbits around a spinning planet in top or 3D view. Jump to the ISS, GPS, geostationary, polar and Moon orbits, read speed, period and energy, check Kepler's third law, and watch an orbit decay.

Circular orbits around a spinning planet: how speed, period and energy depend on radius

Orbits and satellites is a free, browser-based simulation for Cambridge International AS & A Level Physics 9702 (topic 13 Gravitational fields). The course is assessed in Paper 1 (multiple choice), Paper 2 (AS structured), Paper 3 (advanced practical), Paper 4 (A Level structured) and Paper 5 (planning, analysis and evaluation). There are 0 tabs, each a self-contained experiment with its own controls and live readings, and nothing to install: it runs on a laptop, tablet or classroom projector.

Syllabus coverage

• 13.1 Gravitational field: Gravitational field as force per unit mass; Representing fields with field lines; Uniform spheres as point masses at their centres; Newton's law of gravitation: F = Gm₁m₂ ÷ r². Lessons: Gravitational field and Newton's law.
• 13.2-13.3 Gravitational force between point masses and Gravitational field of a point mass: Circular orbits: linking gravitation and centripetal force; Geostationary satellites: 24-hour orbit above the Equator; Deriving g = GM ÷ r²; Why g is approximately constant near Earth's surface. Lessons: Orbits and field strength.
• 13.4 Gravitational potential: Potential as work done per unit mass from infinity; ϕ = −GM ÷ r and the meaning of the negative sign; Gravitational potential energy: Ep = −GMm ÷ r. Lessons: Gravitational potential.

Full syllabus map: A Level Physics 9702 topic 13.

How to use this simulation

1. Use the controls beside the stage to change the set-up and read the live values.
2. The buttons at the end of the tab strip give the scene the whole window (Full screen, Hide controls) and, on a dark stage, a projector-friendly palette (Light scene). Many scenes also have drag handles: drag them to change the set-up directly.

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