Welcome to practical physicsPracticle physics - practical activities designed for use in the classroom with 11 to 19 year olds

Model of planetary path


A demonstration of epicyclic motion.

Apparatus and materials


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.



model used to demonstrate planetary paths

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.
The epicyclic motion of the small sphere can be observed by the class looking edgewise at the model.


Teaching notes


This experiment was safety-checked in April 2007


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