Orbits of planets and satellites sim
Swing the arm of a classroom orbit demonstrator round the Sun one equal step of time at a time, set the orbit's size and shape, predict where a planet on an ellipse is fastest and see why from energy, watch the pull of gravity always point to the centre, then work out v = 2πr ÷ T for satellites from a low orbit to a geostationary one and graph speed against radius.
Orbits: gravity, speed round an ellipse, v = 2πr ÷ T, satellites · covers the IGCSE, GCSE topic
What the sim shows
Model: two bodies, Newton's gravity, the central body fixed. T = 2π√(a³ ÷ GM); the place after each step of T ÷ 24 from Kepler's equation; the speed from energy, v² = GM(2/r − 1/a), so v = 2πr ÷ T on a circle. GM set from round values: 1.5 × 10¹¹ m in 365 days round the Sun, 4.22 × 10⁷ m in 24 hours round the Earth (from memory); not to scale; nothing runs on its own.
- The planet (or satellite) ball, at its place after each equal step of time
- An orbit demonstrator: the central ball is at one focus of every orbit
Use it in your lessons
- Try it here: anyone can unlock 2 figures free, and a free account unlocks up to 5. Runs on a laptop, a Chromebook or a phone; nothing to install.
- Present it and share student links with the teacher plan, from US$5 a month, billed yearly.
- Put it on your own website or LMS for US$9, paid once, or every sim from US$29 a month.
Free guide: 12 practicals as sims, and how to run one in a lesson →
Need a version for your exact set-up? Have one made: US$49 a figure in an order of 5.
More physics sims
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- Three forces in equilibrium: the triangle of forces simHang a load from two newton-meters, read the tensions and the angles, then draw the closed triangle of forces to scale and check it against the meters.
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