Lesson Plan: Escape Speed Physics

This lesson plan includes the objectives, prerequisites, and exclusions of the lesson teaching students how to calculate the vertical speed that an object must have in order to escape the gravitational pull of a planet.


Students will be able to

  • use 𝑣=2𝐺𝑀𝑟 to calculate the minimum escape speed for a planet,
  • understand and interpret graphs of position, speed, or energy against time for projectiles launched vertically from a planet’s surface, including those launched at or near the escape speed,
  • realize that, because a planet has a radial gravitational field, the faster a projectile is launched, the more the shape of its position–time graph deviates from a parabola,
  • recognize an energy–time graph that shows an object escaping a planet’s gravitational pull.


Students should already be familiar with

  • using 𝐸=𝐺𝑀𝑚𝑟 to find the gravitational potential energy of an object in the field of a planet,
  • using 𝐸=12𝑚𝑣,
  • parabolic trajectories in linear fields.


Students will not cover

  • general relativity or any non-Newtonian gravity,
  • the rotation of the planet the object is launched from,
  • routes between orbiting bodies such as planets and moons (i.e., Earth and the Moon),
  • black holes.

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