Earth and Space

Model of planetary path

Practical Activity for 14-16 PRACTICAL PHYISCS


A demonstration of epicyclic motion.

Apparatus and Materials

  • Turntable
  • Small DC motor on a base plate
  • Polystyrene ball
  • Knitting needle
  • Battery, 1.5 V

Health & Safety and Technical Notes

Read our standard health & safety guidance

Make sure that the polystyrene ball is firmly fixed and the sharp point is protected.


  1. Attach the motor base plate to the turntable. When the battery is connected it drives the motor, which rotates a polystyrene sphere in a small circle as shown. At the same time rotate the turntable slowly by hand.
  2. The epicyclic motion of the small sphere can be observed by the class looking edgewise at the model.

Teaching Notes

This experiment was safety-tested in April 2007.

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