Question

Planets and Gravity



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 answers: 1 and 3.

Reason:
- Gravity provides the inward (centripetal) force that, together with inertia, keeps planets and moons in orbit (so statement 1 is correct).
- The Moon orbits Earth while Earth orbits the Sun — both are orbital motions governed by gravity (so statement 3 is correct).

Statements 2, 4, and 5 are incorrect: gravitational force depends on the masses of the objects (F = G m1 m2 / r^2), objects are not fixed but are affected by gravity, and gravity governs the orbits of both planets and moons.