3.7.2.4
Satellite energy: $total energy = KE + GPE stays constant in orbit$
Gravitational Fields & Orbits — AQA A-Level Physics
- A satellite in a stable circular orbit has constant total $energyThe capacity to do work. Measured in joules (J). = KE + GPE$.
- Both KE and GPE individually remain constant for a given orbit radius.
Effect of changing orbit radius
- Smaller orbit (closer to planet): stronger gravitational force, higher speed, higher KE, lower (more negative) GPE, shorter periodThe time taken for one complete oscillation or wave cycle. Measured in seconds (s)..
- Larger orbit (further from planet): weaker gravitational force, lower speed, lower KE, higher (less negative) GPE, longer periodThe time taken for one complete oscillation or wave cycle. Measured in seconds (s)..
Examiner Tips and Tricks
- If you can't remember which way KE and GPE change, think about speed.
- Closer to the planet means a bigger gravitational pull, so a faster orbit and more KE.
- To keep total energyThe capacity to do work. Measured in joules (J). constant, GPE must decrease (become more negative).