Describing How Factors Affect Gravity

Question

In a far-off galaxy, an astronomer observes a moon orbiting a planet. The moon stays in orbit because of the planet’s gravity.

Which scenario would increase the gravity of the planet?

decreasing the distance between the moon and the planet
increasing the distance between the moon and planet
increasing the planet’s inertia
increasing the moon’s inertia

Answer 1

The scenario that would increase the gravity of the planet is decreasing the distance between the moon and the planet.

According to the law of universal gravitation, the gravitational force between two objects is inversely proportional to the square of the distance between them. This means that as the distance decreases, the gravitational force increases.

In contrast:

• Increasing the distance between the moon and the planet would decrease the gravitational force.
• Increasing the planet’s inertia does not directly affect the gravitational force exerted by the planet since inertia is related to the resistance of an object to change in its motion (mass is the more relevant factor when discussing gravity).
• Increasing the moon’s inertia also does not affect the gravity of the planet; gravity depends on the mass of the planet and the distance to the moon.

Therefore, the correct answer is decreasing the distance between the moon and the planet.