Brainlag PlusWhy gravity keeps moons, planets and satellites in orbit, how the velocity can change while the speed stays the same, why closer orbits are faster, and calculating orbital speed with v = 2πr/T.
Gravity bends the path
A moon, a planet or a satellite would travel in a straight line if nothing pulled it.
Gravity pulls it towards the body it orbits, at right angles to its motion.
- In a circular orbit the speed stays the same, but the direction changes all the time.
- Velocity includes direction, so the velocity changes: the object is accelerating towards the centre.
- The resultant force causing this is gravity, acting towards the centre of the orbit.
AQA and OCR test the ideas in this section and the next on Higher papers only. Edexcel tests them on both tiers.
The rest of this lesson and its 10 practice questions are in Plus.
Screen 1 of 5, free to read.
- 10 exam-style questions, marked as you go, each with a worked solution
- The Orbits simulation beside every question
- Anything you get wrong is saved to your flashcards