Non-Circular Orbits (Edexcel GCSE Physics): Revision Note

Non-Circular Orbits

• Some orbits, such as those of comets, are non-circular

  • These are often more elliptical

• However, their orbits are still stable

• For a stable orbit, the radius must change if the comets orbital speed changes

• For example, for a comet in an elliptical orbit around the Sun:

  • As the comet approaches the Sun, the radius of the orbit decreases and the orbital speed increases due to the Sun's strong gravitational pull

  • As the comet travels further away from the Sun, the radius of the orbit increases and the orbital speed decreases due to a weaker gravitational pull from the Sun

Comets travel in highly elliptical orbits, speeding up as they approach the Sun

• As a comet approaches the Sun:

  • It loses gravitational potential energy and gains kinetic energy

  • The icy body of the comet also starts to sublimate, and forms a tail that always points away from the Sun