Planets, springs and pendulums

Abstract

Seeing connections between different areas of physics is a good way to teach physics. In the orbit of a planet, there is a continuous interchange between gravitational potential energy and kinetic energy with the sum being constant. This is essentially the same physics as a mass on the end of a spring, or a pendulum. In this paper, equivalent spring constants are calculated for planetary orbits and the pendulum equation used to derive Kepler’s third law.