6-2, 7-1 review

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Across
  1. 4. The force that allows you to make a turn on a flat surface.
  2. 7. The name of the extra circles added to the Earth-centered models to account for backward motion of the planets.
  3. 9. The name of the type of backward motion of the planets that the Earth-centered model did not account for.
  4. 10. Name of the Polish astronomer who wrote a scientific book about the sun being the center of the solar system in the 16th century.
  5. 11. The name of the model that holds that the sun is the center of the solar system.
  6. 14. This person updated the earth-centered model in the 2nd century AD.
  7. 17. Kepler's _________ Law: The square of the ratio of the periods of any two planets revolving about the sun is equal to the cube of the ratio of their average distances from the sun.
  8. 18. This describes the direction that an object is moving relative to the center of a circle, when it is undergoing circular motion.
Down
  1. 1. The mathematician that was hired by Tycho Brahe to interpret his data.
  2. 2. The first person to propose the sun-centered model.
  3. 3. The name of the acceleration experienced as one goes in a circle.
  4. 5. The person responsible for finding the density (and mass) of the earth. This person is also responsible for finding the universal gravitational constant (G).
  5. 6. The first name of the eccentric astronomer from Denmark who collected 30 years of data and said that the Earth was the center of the solar system, but the planets orbited around the sun.
  6. 8. Name of the way of thinking that says that the Earth is the center of the solar system.
  7. 12. This is the direction that centripetal force always points.
  8. 13. This person proposed a law which states that objects attract other objects with a force that is proportional to the product of their masses and inversely proportional to the square of the distances between them.
  9. 15. Newton's Law of Universal Gravitation said that not only did Earth's gravity pull on an apple, but it pulled on this large object as well.
  10. 16. Kepler's ___________ Law: The paths of the planets are ellipses, with the sun at one focus.