Gravitation 2 Phet Simulations Physics 2010

My Solar System—Lab and WS Name_______________________________

1. Go to: http://phet.colorado.edu/new/simulations/

2. Click the Motion menu item and start the applet “My Solar System.”

3. Move the slider all the way to accurate, click on the tape measure and the grid.

4. Click the radio button for 4 objects and run the simulation until the purple planet (body 2) has made one complete orbit (one year).

5. After the first orbit (year), turn off the traces (show traces box) and watch another orbit (year) of the purple planet (body 2).

Question One:

Is blue moon (body 3) circling the yellow sun (body 1) or the purple planet (body 2)? Explain your answer.

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6. Increase the mass of the sun (body 1) to 400 and allow the simulation to run for one complete orbit of the purple planet (body 2).

7. Decrease the mass of the sun (body 1) to 175 and allow the simulation to run for one complete orbit of the purple planet (body 2). (~90 seconds)

Question Two:

How do the orbits of the planets change when the mass of the sun is increased or decreased? Why? Explain your answer.

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Question Three:

Why does the sun (body 1) follow a circular path? How does the path change as its mass changes? Why? Explain your answer.

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8. Choose the preset for Sun and Planet from the pull-down menu.

9. Complete the data table below by changing the mass as shown and recording the length of the year in seconds, and also measuring the distance from the planet to the sun at the closest point (perihelion) and farthest point (aphelion). (Make sure slider is set to most accurate)

Mass of Sun (body 1)	Mass of Planet (body 2)	Time of One Orbit (planetary year)	Closest Distance to Sun (perihelion)	Farthest Distance to Sun (aphelion)
200	10
400	10
600	10
800	10
1000	10
150	10
200	1
200	20
200	50
200	100
200	200

Question Four:

When is the planet moving fastest? Why?

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Question Five:

What makes the length of the year increase and decrease? Why?

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Question Six:

A planet in a circular orbit would always be the same distance from the sun. What do you notice about orbits with the shortest years? Why?

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10. Choose the ellipses preset from the pull-down menu.

11.You may move the slider bar about 2/3 of the way towards fast for this simulation.

12. Run the simulation until the green planet (body 4) returns to its starting point (one planetary year)

Planet	Time of One Orbit (planetary year)	Closest Distance to Sun (perihelion)	Farthest Distance to Sun (aphelion)
Purple Planet (body 2)
Blue Planet (body 3)
Green Planet (body 4)

14. Change the y velocity of the blue planet (body 3) to 90 and the green planet (body 4) to 70.

15. Run the simulation again until the green planet (body 4) returns to its starting point (one planetary year)

Planet	Time of One Orbit (planetary year)	Closest Distance to Sun (perihelion)	Farthest Distance to Sun (aphelion)
Purple Planet (body 2)
Blue Planet (body 3)
Green Planet (body 4)		estimate

Question Seven:

How does the year of a planet closer to the sun compare with one that is farther away? Why?

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Question Eight:

How can an orbit be made more circular? Explain your answer.

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Question Nine:

In your own words describe what an orbit is and what factors affect the size, speed and time (period) of an orbit.

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