PhET Activity for MS-ESS1-2: My Solar System

DIRECTIONS:
1. You are on the initial screen. Click on the 'Intro' button on the center-left of the screen to open the introduction module.
2. Click the blue 'Play' button located in the top-right panel to start the simulation.
3. Observe the purple planet as it orbits the yellow star.
4. In the right-side panel, check the box for 'Path' to see the trail left by the planet.
Spend 2-3 minutes exploring the default simulation. Observe the stable orbit of the planet around the star without changing any settings. Get comfortable with pausing, playing, and resetting the simulation.

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

DIRECTIONS:
1. Click the orange circular 'Reset' button in the bottom-right corner to return to the default state.
2. Click the blue 'Play' button in the top-right panel.
3. Locate the 'Mass 1' slider in the bottom-left panel, which controls the star's mass.
4. Drag the 'Mass 1' slider to the right, increasing the star's mass to 300.0.

QUESTION: What happens to the planet's orbit when the star's mass is increased?

DIRECTIONS:
1. While the mass slider is still set at 300.0, drag the 'Mass 1' slider in the bottom-left panel to the left, decreasing the star's mass to 150.0. Make sure to press the blue play button.

QUESTION: Decreasing the star's mass causes the gravitational pull on the planet to weaken, making the planet's orbit become (a)   .

DIRECTIONS:
1. Click the orange circular 'Reset' button in the bottom-right corner.
2. In the right-side panel, check the box for 'Gravity Force'.
3. Click the blue 'Play' button.

QUESTION: The gravity force vectors (blue arrows) always point ___ each other, showing that gravity is an ___ force.

(a)  

DIRECTIONS:
1. Ensure the 'Gravity Force' checkbox remains checked and the simulation is playing.
2. Using the sliders in the bottom-left panel, increase the mass of the star ('Mass 1') and the planet ('Mass 2').
3. Set 'Mass 1' to 300.0.
4. Set 'Mass 2' to 75.0.

QUESTION: What is the relationship between the mass of the objects and the magnitude of the gravitational force between them?

DIRECTIONS:
1. Click the orange circular 'Reset' button. (bottom right)
2. In the right-side panel, check the box for 'Center of Mass'. A red 'X' will appear in the middle of the simulation.
3. Press the 'Play' button and observe the motion of the star, planet, and the red 'X'.

QUESTION: In the default system, where the star is much more massive than the planet, describe the location and motion of the center of mass (the red 'X').

DIRECTIONS:
1. Ensure the simulation is running with the 'Center of Mass' box checked.
2. Using the 'Mass 2' slider, increase the planet's mass to its maximum value (200.0).
3. Observe the motion of the star (yellow body) and the center of mass (red 'X').

QUESTION: When the planet's mass is increased to be almost as large as the star's, the star begins to noticeably (a)   around the center of mass.

DIRECTIONS:
1. Click the orange circular 'Reset' button.
2. Using the 'Mass 1' slider, set the mass of the star to its minimum value (e.g., 0.1). This nearly eliminates its gravity.
3. Press the 'Play' button.

QUESTION: According to the model, what path does an object with an initial velocity take through space if there is no gravitational force to alter its course?

DIRECTIONS:
1. Click the 'Lab' tab icon at the bottom of the screen.
2. Click the preset dropdown menu at the top of the right-side panel and select 'Custom'. (It is the last setting)
3. Click the up arrow on the 'Bodies' stepper in the bottom-left panel once to set the number of bodies to 3 (Click through to see how many possible bodies can be added).

QUESTION: The Lab tab allows for creating a ___ system with up to ___ bodies.

(a)  

DIRECTIONS:
1. Without hitting the reset button, check the 'More Data' checkbox in the bottom-left panel to show the data table.
2. Carefully enter the following values into the table for the three bodies:
3. Body 1 (Star): mass = 200, x = 0, y = 0, vx = 0, vy = 0
4. Body 2 (Planet): mass = 10, x = 150, y = 0, vx = 0, vy = 115
5. Body 3 (Moon): mass = 0.1, x = 160, y = 0, vx = 0, vy = 150
6. In the right-side panel, check the 'Path' checkbox.
7. Press the 'Play' button.

QUESTION: In the system you just created, describe the hierarchy of orbits. Which object is at the center of the main orbit, and which object has its own object orbiting it?