Orbital Simulator -- Classroom Activity

The simulator at http://observe.arc.nasa.gov/nasa/education/reference/orbits/orbit_sim.html allows students to investigate Kepler's three laws of planetary motion.  Ask students to work in small groups to explore the simulator, and to keep a record of what they do.  On the Third Law simulation, bear in mind that the relationship (period squared) ~ (radius cubed), when translated into mean orbital speed, becomes (speed squared) ~ (1/radius), so a smaller radius implies a higher speed. 

The following are possible questions for classroom discussion: 

A. First simulator: The Law of Ellipses:

  • At what point does the satellite move the fastest?
  • At what point does the satellite move the slowest?
  • The Earth is at one focus of the ellipse.  What is at the other focus?
  • What does the orbit look like if the eccentricity is set at one of the values for a planet about the Sun?
B. Second simulator: The Law of Areas:
  • Which end of the ellipse is the yellow section thinnest on?
  • Which is it the thickest?
  • The yellow section shown will always be the same area, although sometimes it is thinner and sometimes it is thicker.  How can this be the same area, yet have a different shape? (You might have to demonstrate conservation using the same amount of liquid in two differently shaped cups.)
C. Third simulator: The Harmonic Law:
  • How does the period of revolution of the Shuttle compare with that of a geosynchronous satellite?  With the period of the Moon?
  • While the space shuttle orbits the earth, it doesn’t speed up or slow down by accelerating like a car.  Instead, it moves to a higher or lower orbit.  What does it need to do if it wants to speed up?
  • What does it need to do to slow down?