This key facts covers What Keeps Objects in Orbit? within Orbits for GCSE Physics. Revise Orbits in Space Physics for GCSE Physics with 13 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.
📚 What Keeps Objects in Orbit?
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.
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