AST 307 · Introductory Astronomy
Fall 2003


Chapter 2  Sep. 5-10

  1. Describe the motions of the planets on the celestial sphere, and use the Copernican (heliocentric) model to explain their prograde and retrograde motions.

  2. State Kepler's three laws of planetary motion.

  3. Define: aphelion, perihelion, semi-major axis.

  4. Be able to use Kepler's 2nd law to compare the speed of a planet at perihelion to its speed at aphelion.

  5. State Newton's three laws of motion and his law of gravity.

  6. If a planet orbits the Sun on a circular orbit: does its speed change?
    is it accelerating?
    what force or forces are acting on it and in what direction?
    how does the force it exerts on the Sun compare to the force the Sun exerts on it?

  7. Explain how Newton's laws can be used to derive Kepler's 3rd law and how the result differs from Kepler's law.

  8. Describe the concepts of kinetic and potential energy and describe how they can be used to calcuate the escape speed from a planet.

9 September 2003
Astronomy Program · The University of Texas at Austin · Austin, Texas 78712
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