• 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 Oa each other?
• How can the Sane gravitational attraction account for the orbital motion of the planets?
• What forms of energy axe 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?