A planet on a circular orbit travels the whole way round in one period. Divide that distance by the time and you have its speed, which is why the inner planets, on tighter loops, race round so much faster.
An orbiting body moves at v = 2 pi r divided by T, the circumference of the orbit divided by the time for one orbit. Planets closer to the Sun travel faster and take less time to go round.
The orbital speed of a body in a circular orbit is the circumference of the orbit divided by the orbital period T.
Planets closer to the Sun have higher orbital speeds and shorter periods.
Change the orbital radius and period and watch the orbital speed that results.
Four quick checks. Each correct answer earns XP and lights this skill on your star map.
The orbital speed of a body in a circular orbit is given by...
In v = 2πr ÷ T, the symbol r stands for the...
In the formula, the quantity 2πr is the...
Compared with planets far from the Sun, planets close to the Sun have...
The distance for one orbit is the circumference 2 pi r, and dividing by the period gives the speed.
The Earth orbits the Sun at a radius of about 1.5 × 10¹¹ m, taking 3.15 × 10⁷ s for one orbit. Find its orbital speed.
Use the full circumference 2 pi r, not just the radius, and keep r in metres and T in seconds. Planets further from the Sun move more slowly and take longer to orbit.
Unlocks once the four checks above are done. Worth more XP, written in the style of Paper 2.
In the orbital-speed formula, 2πr represents the...
A moon orbits at a radius of 3.0 × 10⁷ m with a period of 2.0 × 10⁴ s. Its orbital speed is about...
Two planets orbit the same star. Compared with the more distant one, the closer planet has...
Orbital speed is mapped. Keep the chain going.