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Orbital velocity
Intermediate
Speed of a circular orbit.
v_o = √(GM/r)For a circular orbit, gravity supplies the centripetal force: GMm/r² = mv²/r, so v = √(GM/r). Low Earth orbit speed is about 7.8 km/s.
At 400 km altitude: 7.67 km/s.
Higher orbits are slower.
In more detail
The orbital velocity of a satellite in a circular orbit is v = sqrt(GM/r). It depends on the radius only, so lower orbits are faster.
Real-world uses
- Low Earth orbit satellites travel at about 7.8 km/s.
- Space stations need precise speed to maintain their altitude.
- Satellite operators calculate the speed needed to keep a spacecraft in a circular orbit at a given height.
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Frequently asked questions
Why do satellites in lower orbits go faster?
Because stronger gravity at lower altitudes must be balanced by greater speed for a circular path.
Does satellite mass matter?
No, orbital velocity does not depend on the satellite's own mass.
Why does a satellite not fall to the ground?
It falls continuously, but its sideways velocity is enough that the Earth's surface curves away beneath it.
Related topics in Gravitation & Orbits
Field inside a uniform sphere · Escape velocity · Escape velocity of Earth · Satellite energy · Orbital period · Geostationary satellites