Kepler’s Laws Simulation
Lab
Student Learning Objectives:
Understand Kepler’s three laws of planetary motion.
Lab simulation time: 40 minutes
This is a "virtual lab". We will do an experiment using software, which can be found at
the PhET simulations page: http:phet.colorado.edu
Find the sim "My Solar System” and run it. You should see this:
0) Play with this simulation to get a feel for the variable and controls.
Kepler’s First Laws
1. Using Select Preset, select “Sun and Planet”. Then select, System centered, Show
Traces, and Show Grid. Describe the shape of the orbit.
2. Move the planet slightly outward without changing the velocity. Run the simulation.
Repeat two more times. What changes about the shape of the orbit as the radius is
increased?
3. Try different velocity settings and different orbital distance to see how each determines
the shape of the orbital pathway.
4. What factors influence the shape of the orbital pathway?
Kepler’s Second Law
1. Using the variables, create an orbital that is very elliptical, but still stays on the screen.
2. Observe the relative velocity of the planet and aphelion and perihelion. What is the
relationship between the two velocities?
3. Try at least two more elliptical orbits. Does the same relationship hold true for the
relationship between the two velocities?
4. Do your findings agree with Kepler’s Second Law? Why or why not?
Kepler’s Third Laws
1. Activate the ruler tool. You will use this tool to measure the radius of the planets orbit
around the Sun.
2. Using different speeds and radii, record the orbital period, radius at aphelion, and
radius at perihelion in the data table below.
Period of Orbit (T)
Radius at Aphelion
Radius at
Perihelion
Semi major Axis of
Orbit
3. Determine the semi major axis of orbit using the average of the radius at aphelion and
perihelion.
4. Create a graph of T and R that should produce a straight line. What factor of T and
R will you use?
5. Be sure to create a graph and upload it to the lab dropbox. Save the file as a jpg file so
it will fit. If you wish to save the picture as a jpg and then insert into this document, that
is fine also.
6. Using your graph determine the mass of the Sun in this experiment. This will not be
the correct value of the Sun’s mass because time is not given in seconds, and the radius is
not in meters. We are looking for the correct calculations, not the correct answer. Please
show all of your work.