Gravity provides the centripetal force:
- An orbiting object is constantly changing direction (curved path)
- Changing direction = changing velocity = acceleration
- This acceleration is caused by gravitational force pulling towards the centre
- Gravity acts as the centripetal force — always pointing towards the central body
💡 Key insight: The object doesn't fall INTO the planet because its sideways velocity is great enough to keep "missing" as it falls.
This key facts covers What Keeps Objects in Orbit? within Orbits for GCSE Physics. Revise Orbits in Space Physics for GCSE Physics with 14 exam-style questions and 10 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 2 of 8 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Orbits
What is a protostar?
Explain why a main sequence star remains stable (in equilibrium) for billions of years.
Quick recall flashcards
What is a polar orbit used for?
Mapping - the satellite orbits at ~800 km altitude covering the whole Earth as the planet rotates beneath it
What is Low Earth Orbit (LEO)?
Orbit at 200-2000 km altitude with ~90 minute orbital period. Used for ISS, imaging, and Earth observation