Jupiter is the most massive planet in the solar system. Earth has much less mass than Jupiter, and Mercury has much less mass than Earth. Suppose a spaceship was orbiting at a distance of 20,000 km above the surface of Jupiter. How far away from Mercury would the spaceship have to orbit to experience the same gravitational force?
A. Exactly 20,000 km away.
B. Less than 20,000 km away.
C. More than 20,000 km away.
D. Halfway between Mercury and Jupiter.

Question

Jupiter is the most massive planet in the solar system. Earth has much less mass than Jupiter, and Mercury has much less mass than Earth. Suppose a spaceship was orbiting at a distance of 20,000 km above the surface of Jupiter. How far away from Mercury would the spaceship have to orbit to experience the same gravitational force?
A. Exactly 20,000 km away.
 B. Less than 20,000 km away.
 C. More than 20,000 km away.
 D. Halfway between Mercury and Jupiter.

Shadow · Answer

What’s your thought process for this one? It relates back to things I said in the last problem.

Mal87 · Answer

I was thinking less than 20,000km away.

Shadow · Answer

What made you think of that answer?

Mal87 · Answer

I thought it was going to be less than because of the gravity and there is no velocity because it does not move.

Shadow · Answer

Your answer is correct, thought I’m not sure you understand why it is correct. If Mercury has less mass than Jupiter, the spaceship would need to be far closer to Mercury than it was to Jupiter in order to experience the same gravitational force. This is because more mass = more gravitational force. Since we can’t increase the mass of a planet, we simply get close to it. Decreasing the distance between objects increases gravitational force.

Mal87 · Answer

That makes much more since then my explanation.

Shadow · Answer

Perhaps I can think of an analogy to help you better remember it, haha