GCSE Physics (AQA)

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Orbital Speed

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Space physics Solar system; stability of orbital motions; satellites

Orbital Speed

6:34 Orbits
Spec 4.8.1.3
Previous Orbits & Circular Motion Next Stable Orbits
  • The closer a planet or satellite is to the object it is orbiting, the stronger the gravitational force acting on it.
  • A satellite or planet will orbit when gravitational forces keep them traveling in a circular path.
  • Mercury, being closer to the sun, experiences a stronger gravitational force than Venus, which is further away.
  • The stronger the gravitational force, the faster an object will move in its orbit.
  • Mercury moves faster (48 km/s) than Venus (35 km/s) due to stronger gravitational forces.
  • Orbital speed can be calculated using the radius of an orbit and the time taken to complete it.
  • Earth's orbit speed can be calculated using its orbital radius (150 million km) and time (365.25 days).
  • Earth travels at 2.6 million km/day, or 30,000 m/s.
  • The speed of planets varies; further planets from the sun move slower due to weaker gravitational forces.
  • Understanding the relation between radius, force, and speed is important for choosing orbits of artificial satellites.
  • Polar satellites move quickly in low orbits to cover much of Earth's surface.
  • Geostationary satellites move slowly in far orbits to match Earth's rotation.
  • The link between a satellite's orbit and its speed should be understood, though specific satellite types need not be recalled for exams.

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