Earth & Moon: Set Up Inequality

[harpazo]

According to Newton's universal gravitation, the attractive force F between two bodies is given by F = G[(m_1*m_2)]/r^2 where m_1 and m_2 are the mass of the two bodies, r is the distance between the two bodies, and G is the gravitational constant 6.672 • 10^(-11)newtons meter squared kilogram squared.

Suppose an object is traveling directly from Earth to the moon. The mass of Earth is 5.9742 • 10^(24) kilograms, the mass of the moon is 7.349 • 10^(22) kilograms and the mean distance from Earth to the moon is 384,000 kilometers. For an object between Earth and the moon, how far from Earth is the force on the object due to the moon greater than the force on the object in terms of Earth?

 

[MarkFL]

This is mathematically identical to the "Planet A/Planet B" problem. What I would suggest is for you to derive a general formula that you can then apply to both problems. Work smart, not hard.

 

[Otis]

@harpazo: Did you post this exercise because you need help with it? I'm asking because (as Mark noted above) it's the same as the other exercise. In the other thread, you told us that you would finish that exercise on paper and post only if you got stuck. You did not post anything, so it seems like you finished it with no issues. If you've finished the first one, then you ought to have shown how far you got on this one.

Do you have any work to show on the exercise above? Where exactly are you stuck?

If you haven't yet finished the first exercise, then why did you start this one?

Please don't say that you've posted this second exercise for other students to practice. (We've told you: This forum doesn't need to collect or offer practice exams or exercises because a lot of other free sites already do that.)

 

[harpazo]

@harpazo: Did you post this exercise because you need help with it? I'm asking because (as Mark noted above) it's the same as the other exercise. In the other thread, you told us that you would finish that exercise on paper and post only if you got stuck. You did not post anything, so it seems like you finished it with no issues. If you've finished the first one, then you ought to have shown how far you got on this one.

Do you have any work to show on the exercise above? Where exactly are you stuck?

If you haven't yet finished the first exercise, then why did you start this one?

Please don't say that you've posted this second exercise for other students to practice. (We've told you: This forum doesn't need to collect or offer practice exams or exercises because a lot of other free sites already do that.)

I'll take care of it.