This study notes covers Orbital Speed and Radius 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 4 of 8 in this topic. Use this study notes to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 4 of 8
Practice
13 questions
Recall
10 flashcards
🛰️ Orbital Speed and Radius
The key relationship:
- Orbit closer to planet → need to move FASTER to stay in orbit
- Orbit further from planet → move SLOWER
- The Moon orbits slowly (~1 km/s); the ISS orbits fast (~7.7 km/s) — ISS is much closer!
Why? Closer = stronger gravity = need more speed to avoid falling in. Further = weaker gravity = less speed needed.
Orbital period and radius:
- Larger orbital radius = longer orbital period (takes longer to complete orbit)
- Mercury (closest to Sun) = 88 days; Neptune (furthest) = 165 years
Keep building this topic
Read this section alongside the surrounding pages in Orbits. That gives you the full topic sequence instead of a single isolated revision point.
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
13 questions on Orbits — practise free
Instant marking, adaptive difficulty, and 10 spaced repetition flashcards. Free until your GCSEs.
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