Expert answer:A model of a planetary system

Solved by verified expert:Understand Kepler’s Laws of orbital motion. Discover how the distance and planet’s tangential speed affects the shape of the orbit. Measure the change in orbital period as distance is increased. Apply concepts relating to Kepler’s Laws to speculate conditions that lead to a stable planet environment for evolution of life.
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Physics PhET Lab:
A model of a planetary
system
NAME ________________________
Student Learning Objectives:
1. Understand Kepler’s Laws of orbital motion.
2. Discover how the distance and planet’s tangential speed affects the shape of the
orbit.
3. Measure the change in orbital period as distance is increased.
4. Apply concepts relating to Kepler’s Laws to speculate conditions that lead to a
stable planet environment for evolution of life.
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: https://phet.colorado.edu/en/simulation/legacy/my-solarsystem
Click on the simulation to run it (you do not need to download it). You should see this:
0) Play with this simulation and “mouse” around with it. Try to figure out what all the
controls do.
1) Using Select Preset, select “Sun and Planet”. Then select, System centered,
Show Traces, and Show Grid. Determine responses to the questions below by
running the simulation.
a)What are the preset values for: the mass of the star, the mass of the planet, the distance,
and the velocity?
b) Describe the shape of the orbit.
c) How does the distance and planet tangential speed affect the shape of the orbit?
(Distance and tangential speed for the planet can be changed by editing the pink position
x box and the pink velocity y box.)
10/31/2017
Astronomy-Physics: Gravitation
Edit of Original by Mark Kelly
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2) Click the “Reset” button. Set the masses of Body 1 and Body 2 and the velocity of
Body 2 to the initial values you noted in 1). Now, set the distance between the star and
planet to 100. Run the simulation as above. Record the distance and orbital period in the
table on the next page. Move the planet outward, in increments of 10, and observe (and
record) the orbit period. Do not move the planet past 200. (As the distance increases, you
may want to move the slider so that it is midway between the center and “fast”.)
Make a graph of distance (from the star) vs. period of orbit using the data you
record in the table. (Use the graph paper on the last page or create a graph using
Excel. Label the axes and use a scale that makes sense. Draw a smooth curve
through your data points.)
[A few notes on making a graph:
The y-axis on the graph is the vertical axis (up and down)
The x-axis on the graph is the horizontal axis (side to side)
Graphs are always titled as “Something vs. Something else”.
The “something” is plotted along the y-axis.
The “something else” is plotted along the x-axis.
First comes y, and then comes x. Think of it that way.]
Distance
Orbital Period
100
110
120
130
140
150
160
170
180
190
200
3) What happens to the period as the star-planet distance increases? Why do you think
there is a relationship?
4) Using Select Preset, select “Ellipses”. Run the simulation. Record your observation
of planet orbital speed as a function of distance from the star.
• You can find values by using the “Tape Measure” tool.
• Place the body of the tape measure at the center of the star and use your mouse to
“pull” the other end to measure the distance to the planets.
• Run the simulation and stop it at some point.
• Then measure the distance to each planet and record the value in the table.
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Astronomy-Physics: Gravitation
Edit of Original by Mark Kelly
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• Mouse over each planet to find the x velocity and y velocity values. Record these
also. Do this at least three times, measuring the planets at different points in their
orbits.
• Use the equation Orbital Speed = √( )2 + ( )2 to find the
Orbital Speed. (Don’t forget! First, square values, then add them, then take the
square root!)
• Evaluate the observations you recorded.
Write a quantitative and qualitative explanation for behavior you see.
Planet
Distance
x velocity
y velocity
Orbital Speed
Pink
Blue
Green
5) Astronomers believe that terrestrial planets in binary star system could not support
advanced life. (hint: Dole (1964) estimated that the average amount of energy received by a
planet not could vary by more than 10 % without affecting its habitability).
•
•
•
•
•
Select “Binary Star, planet”, note the initial conditions (masses, distances, and
velocities), and run simulation for a few minutes (real time).
Think about what occurred in the simulation and what changes might be made to
try to make a stable system. In particular, try to create a stable system in which
the planet would receive a fairly constant amount of energy from the star(s).
Create a computer simulation that you believe meets the criteria mentioned above.
Run your simulation to test.
Carefully describe the initial conditions of the simulation, your observations, and
conclusions that support or refute this hypothesis. (Note that light follows an
inverse square law just as gravity does. The amount of light received from a star
falls off as 1 / (distance)2.)
10/31/2017
Astronomy-Physics: Gravitation
Edit of Original by Mark Kelly
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10/31/2017
Astronomy-Physics: Gravitation
Edit of Original by Mark Kelly
…
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