Final answer:
The correct answer is that the net force on the Moon preventing it from falling to Earth is gravitational. This gravitational force acts as the centripetal force that maintains the Moon's orbit around Earth, in accordance with Newton's law of universal gravitation.
Step-by-step explanation:
The question "The moon does not fall to the earth because the net force is:" relates to understanding why the Moon remains in orbit around the Earth instead of falling into it. The answer to this question is that the net force is gravitational, option d). This means the gravitational force is the centripetal force that keeps the Moon in its orbit, balanced by the Moon's inertia which tries to move it in a straight line, resulting in a stable orbit. Here's a little bit more insight:
- Option a) Attractive: While gravitational force is indeed attractive, this option is too vague since it does not acknowledge that this attractive force is balanced by the Moon's inertia.
- Option b) Zero: The net centripetal force is not zero; the gravitational force acts as a centripetal force, causing the Moon to orbit Earth rather than fall straight towards it or fly off into space.
- Option c) Repulsive: There is no repulsive force between the Earth and the Moon; their interaction is purely gravitational.
- Option d) Gravitational: Correct. The gravitational force between Earth and the Moon provides the necessary centripetal force for the Moon's orbit.
This explanation is in line with Newton's law of universal gravitation, which states that every mass attracts every other mass with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between their centers.