Orbital speeds of planets and satellites
2 marks · EasyA satellite orbits a planet at a constant radius of 10,000 km and completes one orbit every 20,000 seconds. Calculate its average orbital speed in km/s. Give your answer to 2 significant figures.
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3.1 km/s (±0.1)
Common mistakes: Forgetting to use circumference formula; Using diameter instead of radius
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Marking points
M1 · 1 mark · Substitutes correct values into v = 2πr / T (with r = 10,000 km, T = 20,000 s).
A1 · 1 mark · Correct final answer to 2 significant figures: 3.1 km/s.
Worked solution
The orbital speed is given by: