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Gravity and Motion

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I derive from the celestial phenomena the forces of gravity with which bodies tend to the sun and the several planets. Then from these forces, by other propositions which are also mathematical, I deduce the motions of the planets, the comets, the moon, and the sea.

Isaac Newton

Questions to Explore:
  • How are forces related to motion?
  • What are momentum and angular momentum? What do they have to do with motion and the orbits of the planets?
  • What factors control the gravitational forces objects exert on each other?
  • How can the Sun’s gravitational attraction account for the orbital motion of the planets?
  • What forms of energy are important for an orbiting planet?
  • What is meant by escape velocity?
  • Why do tides occur and where can the strongest tides be found? What effect do tides have on the Earth and its oceans?

AstronomyOnline Learning Center

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