Question

A student is investigating the role of gravity in the orbital motion of objects within Earth's solar system. He creates a model, not to scale, to help with his investigation. His model shows that planets and moons are held in their orbit through gravity, an inward-pulling force, and through inertia, the tendency of an object to resist change in direction and speed. His model is shown.



From left to right, the model shows the Sun, Mercury, Venus, Earth, Mars, the asteroid belt, Jupiter, Uranus, and Neptune. The model also shows each planet in its orbit around the Sun and the moons that orbit each planet.



He also creates a table with the masses of the planets and their distances from the Sun.



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Which TWO statements are correct about the motion of objects in the solar system?


All objects in the solar system are held in orbits due to gravity.


Gravitational force is independent of the mass of the objects.


The Moon orbits around Earth, while Earth orbits around the Sun.


All objects in the solar system are in fixed positions and are not affected by gravity.


Gravitational pull causes motion of planets, not moons, in their orbits.

Answer 1

Correct choices:
- All objects in the solar system are held in orbits due to gravity.
- The Moon orbits around Earth, while Earth orbits around the Sun.

Brief justification:
- Gravity provides the centripetal force that (together with the objects' inertia) keeps planets, moons, asteroids, etc. in orbit.
- The Moon is bound by Earth's gravity and orbits Earth; Earth (and the Moon–Earth system) orbits the Sun.

(The other statements are incorrect: gravitational force depends on the masses involved, objects are not fixed in position, and gravity holds both moons and planets in their orbits.)