Lesson Plan: Kepler’s Third Law of Planetary Motion Physics • 9th Grade

This lesson plan includes the objectives, prerequisites, and exclusions of the lesson teaching students how to use Kepler’s third law of planetary motion to find the orbital characteristics of planets and satellites.


Students will be able to

  • find 𝑇𝑎 for any orbiting object given 𝑇 and 𝑎,
  • find 𝑇𝑎 for any orbiting object given the mass of the host,
  • use 𝑇𝑎=𝑇𝑎 in all permutations,
  • use 𝑇𝑎=4𝜋𝐺𝑀 in all permutations.


Students should already be familiar with

  • astronomical units,
  • elliptical orbits,
  • the structure of the solar system.


Students will not cover

  • Kepler’s second law,
  • any non-Newtonian gravity.

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