Question

although neptune is the farthest planet from the sun, it travels in a fixed orbit around the sun and never changes its path. what is the reason for this?
a the gravitational pull of the sun holds neptune in its orbit
b the magnetic pull of the sun holds neptune in its orbit.
c the nuclear force acting between the sun and neptune holds the latter in its orbit
d the repulsive force of bodies outside the solar system holds neptune in its orbit

Explanation:

• Option A: Newton's law of universal gravitation states that every object in the universe attracts every other object with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. The Sun has a large mass, and the gravitational pull between the Sun and Neptune keeps Neptune in its orbit.
• Option B: The magnetic pull is not the main force that keeps planets in orbit. Magnetic forces are significant in some specific contexts (e.g., within magnetic materials or in some astrophysical phenomena like solar flares interacting with Earth's magnetosphere in a complex way, but not for planetary - orbital motion).
• Option C: Nuclear forces (strong and weak nuclear forces) act at very short distances (on the order of atomic and sub - atomic scales). They have no role in the large - scale motion of planets in the solar system.
• Option D: Bodies outside the solar system are too far away, and their forces (if any) are negligible compared to the gravitational force of the Sun on Neptune. Also, a repulsive force from outside the solar system would likely disrupt Neptune's orbit rather than keep it in a fixed path.

Answer:

A. The gravitational pull of the Sun holds Neptune in its orbit