PhET Activity for MS-ESS1-3: Gravity & Orbits

DIRECTIONS:
1. Click on the 'Model' button on the initial screen.
2. Press the large blue play button at the bottom of the screen to start the simulation.
3. Observe the planet orbiting the sun.
4. Use the play/pause button to start and stop the motion.
5. On the right panel, check and uncheck the boxes for 'Velocity', 'Path', and 'Grid' to see what they do.
Spend 2-3 minutes exploring the simulation. Try the playback controls and the checkboxes on the right. Do not change any mass sliders or move the objects yet.

QUESTION: Are you acquainted with the tools in this simulation?

DIRECTIONS:
1. Click the circular arrow 'Reset' button in the top right panel.
2. Press the play button to start the orbit.
3. After the planet has moved for a few seconds, click the 'off' option on the 'Gravity' switch in the right panel.

QUESTION: What happens to the planet when gravity is turned off?

DIRECTIONS:
1. Click the big orange 'Reset' button in the bottom right corner. This will also turn gravity back on.
2. Check the box for 'Gravity Force' in the right panel.
3. Press the play button.

QUESTION: The blue gravity force arrows always point from the center of the planet towards the center of the ___ and from the center of the sun towards the center of the ___.

(a)  

DIRECTIONS:
1. Ensure the 'Gravity Force' box is still checked from the previous slide.
2. Now, check the box for 'Velocity' in the right panel.

QUESTION: The planet's velocity vector is always (a)   to the curved orbital path.

DIRECTIONS:
1. Click the small 'Reset' button in the top right corner.
2. In the right panel, move the 'Star Mass' slider all the way to the right, setting it to 2.0.
3. Check the boxes for 'Path' and 'Gravity Force'.
4. Press the play button.

QUESTION: When the star's mass is doubled, what happens to the gravitational force and the planet's orbit?

DIRECTIONS:
1. Click the small 'Reset' button in the top right corner. This will reset the star's mass to its default value (Our Sun).
2. Move the 'Planet Mass' slider all the way to the right, setting it to 2.0.
3. Check the 'Path' box.
4. Press play and observe the orbit.

QUESTION: Describe what you observed when you doubled the planet's mass. Did it significantly change the planet's orbital path around the sun? Why do you think this is?

DIRECTIONS:
1. Click the small 'Reset' button in the top right corner.
2. Check the 'Velocity' and 'Path' boxes if not already done.
3. With the simulation paused, click and drag the tip of the green velocity arrow to make it about half its original length without changing its direction.
4. Press play and observe the path.
5. Reset the simulation again. This time, drag the velocity arrow to make it about 50% longer again without changing its direction.
6. Press play and observe the path.

QUESTION: Match the initial velocity setting with the most likely outcome for the planet's orbit.

DIRECTIONS:
1. Click the big orange 'Reset' button in the bottom right corner.
2. From the presets menu in the top right, select 'Sun, Planet, Moon'.
3. Check the 'Path' box.
4. Press the play button.

QUESTION: In this system, the planet orbits the ___, while the moon orbits the ___.

(a)  

DIRECTIONS:
1. Switch to the 'To Scale' tab at the bottom of the screen.

2. 2. Click the 'Sun, Planet, Moon' system in this new view.
   2. Observe the positions and sizes of the objects in this new view.
   
   QUESTION: What is the primary purpose of the 'To Scale' mode compared to the 'Model' mode?

DIRECTIONS:
1. Click the orange 'Reset' button in the bottom right corner to ensure default settings.
2. Select the 'Planet, Moon' preset from the top right panel and check the 'Path' box.
3. Press play and observe the default orbit. Then, pause the simulation.
4. Move the 'Moon Mass' slider to the maximum value (2.0).
5. Press play and observe the Moon's path.

QUESTION: Does changing the mass of the orbiting body (the Moon) have a large, noticeable effect on its own orbital path? Briefly explain your observation.