Download `Gravity Force` box and run the simulator for another complete orbit

Gravity and Orbits activity
Name__________________________
Directions: Download the Gravity and Orbits simulator from the PhET website:
https://phet.colorado.edu/en/simulation/legacy/gravity-and-orbits
Answer the following questions using the simulator as instructed.
Earth and Sun only
1. Check the box labeled 'Path' and run the simulator at whatever speed you choose for one complete orbit (365
Earth days.) Describe the shape of the orbital path.
2. Check the 'Gravity Force' box. Run the simulator for another complete orbit. How would you describe the
direction of the force? Does the magnitude of the force change?
3. Keep the 'Gravity Force' box checked and check the 'Velocity' box as well. Run the simulation. How would
you describe the direction of the velocity relative to the direction of the gravity force? Does the magnitude
change? If so, when is it the fastest and when is it the slowest?
4. Reset the simulation and increase the size of the sun so that it is set to the 3rd hash mark (second from the
right.) Check only the 'Path' box. Leave the rest unchecked. Run the simulator for one complete orbit and
describe the shape of the orbital path.
5. How many Earth days are needed for one complete orbit with the increased mass of the sun?
6. Check the 'Gravity Force' box and run the simulator for another complete orbit. How would you describe the
direction of the force? Does the magnitude of the force change?
7. Check the 'Velocity' box and run the simulator for another complete orbit. Does the magnitude of the velocity
change? If so, when is it the fastest and when is it the slowest?
8. What effect does changing the size of the planet have on the number of days for the orbital period?
Earth with International Space Station
9. What is the orbital period for the ISS?
10. Why is the orbital period so much shorter than the Earth orbiting the sun?
Earth with the Moon
11. Would you expect the moon's orbital period around the Earth to be closer to that of the Earth around the sun
or the ISS around the Earth? Justify your answer.
12. Test your prediction by running the simulation involving the Earth and the moon. Was your prediction
accurate?
13. What two factors affect orbital period?
Sun, Earth, and Moon
14. Check the 'Path' box only. Run the simulation for one complete orbit. Why does the moon travel in a flower
pattern? Does the distance between the Earth and the moon change?
15. Would a year on Mars be longer, shorter, or the same as a year on Earth? Explain.
*16. Using the Earth and Sun simulation, change the settings to achieve the longest and shortest orbital periods.