1. Which of the following statements best describes the role of gravity in keeping the moon in orbit around Earth?

• Earth’s gravitational force pulls the moon towards Earth’s center.
• The moon’s gravitational pulls the moon toward Earth's surface of earth.
• The sun’s gravity keeps the moon in orbit around Earth.
• Gravity from the moon and earth push against each other to keep the the moon in an orbit around Earth.

2. What would most likely happen to the motion of the planets if the sun, and its gravitational pull, were to suddenly disappear?

• The planets would come together, towards the space where the sun had been.
• The planets would continue in their orbits. Nothing would change.
• The planets would all begin to move away in straight paths into space.
• The planets would continue to move in circular orbit, but the orbits would grow larger as the planets moved outward from the center of the solar system.

3. Your classmates are discussing what would happen to the strength of Earth’s gravitational pull on the moon if the two objects were to begin moving farther apart from each other. Which student’s claim is correct?

• “Distance doesn’t have anything to do with gravitational pull, since it really just depends on the mass of the two objects.”
• “Earth’s gravitational pull on the moon would get stronger if the two objects moved farther apart.”
• “Earth’s gravitational pull on the moon would grow weaker as the distance between the objects increased.”
• “Earth’s gravitational pull on the moon would have a sort of yo-yo effect. The moon would move farther away and then it would change direction and get pulled back in towards Earth.”

4. How would the gravitational force between two objects be affected if the mass of one of the objects were to increase?

• The gravitational force between the objects would decrease.
• The gravitational force would increase for a while before returning to the same strength as it was before.
• The gravitational force between the objects would remain the same.
• The gravitational force between the objects would increase.

5. Which of the following statements accurately describes a relationship suggested by the data in the table?

• The distance of a moon from a planet will affect that moon’s orbital velocity.
• Moons that experience an increased gravitational force will orbit their planets at a higher velocity.
• Moons that experience an increased gravitational force will orbit their planets at a lower velocity.
• The size of a planet’s moons indicates the strength of that planet’s gravitational force.

6. Which piece of data in the table suggests that distance affects the magnitude of an object’s gravitational pull?

• The orbital velocity of Earth’s moon is less than any of the moons of Jupiter.
• The mass of Jupiter’s moons increases as their distance from Jupiter increases.
• The orbital velocity of Jupiter’s moons decreases as their distance from Jupiter increases.
• Earth’s moon is closer to Earth than any of the Galilean moons are to Jupiter.

7. Which piece of evidence in the table supports the claim that an object’s gravitational pull depends on the object’s mass?

• There is no evidence in the table to suggest that there is a relationship between mass and gravitational force.
• Jupiter’s moons all have a higher orbital velocity than Earth’s moons due to Jupiter’s increased mass and therefore increased gravitational pull.
• Earth’s moon has the smallest mass and therefore has the slowest orbital velocity due to a weaker gravitational pull.
• Jupiter’s most massive moon has a higher orbital velocity than any of Jupiter’s other moons and therefore has a stronger gravitational pull.

8. A classmate claims that if Jupiter’s Galilean moons were all the same distance from Jupiter, they would all experience the same amount of gravitational force. Using what you have learned and the evidence from the data table, how would you respond to his claim?

• His claim is incorrect; if the moons were at an equal distance from Jupiter, then the pull of gravity would be the strongest on Ganymede because it is the largest moon.
• His claim is incorrect; if the moons were at an equal distance from Jupiter, then the pull of gravity would be the strongest on Ganymede because it has the greatest mass.
• His claim is correct; if the moons were all at an equal distance from Jupiter, then the pull of gravity from Jupiter would be experienced equally by all four moons.
• His claim is incorrect; if the moons were at an equal distance from Jupiter, then the pull of gravity would be the strongest on Europa because it has the smallest mass.

9. One of your classmates observes that Io is roughly the same size and mass as Earth’s moon, and although its distance from Jupiter is farther than Earth’s moon’s distance from Earth, it has a significantly higher orbital velocity. Using what you have learned, and the data from the table, to help explain this discrepancy in the two moons’ orbital velocities.

• Io orbits at a much higher rate because Jupiter is so much larger than Earth. Therefore if it didn’t move so fast it would take too long to complete one orbit.
• Io orbits at a much higher rate because Jupiter has a much greater mass than Earth and therefore has a stronger gravitational pull.
• Io orbits at a much higher rate because its orbit is influenced by the masses of the other 3 Galilean moons.

10. A classmate states that, due to Jupiter’s increased mass, it exerts a stronger gravitational force on its moons than Earth exerts on Earth’s moon. Explain how the data in the table provides evidence to support her claim.

11. Explain how the data provides evidence that both mass and distance affect the strength of an object’s gravitational force.