# Gravitational potential

The image below shows a sketh of gravitation potential (y axis) vs. position:

http://img175.imageshack.us/img175/5717/60413547vb3.th.jpg [Broken]

Can someone please explain why the potential does not equal zero at the neutral point - wouldnt the two potentials cancel each other out?

Thanks

Last edited by a moderator:

## Answers and Replies

D H
Staff Emeritus
Science Advisor
Can someone please explain why the potential does not equal zero at the neutral point - wouldnt the two potentials cancel each other out?
First off, why would you expect it to go to zero? That plot is of

$$u(r) = -\left(\frac{GM_e}{|r|} + \frac{GM_m}{|R_m-r|}\right)$$

That function is negative definite: its value is negative for all finite values of r.

Secondly, what do you mean by "neutral point"? This term has multiple meanings.

tiny-tim
Science Advisor
Homework Helper
The image below shows a sketh of gravitation potential (y axis) vs. position:

http://img175.imageshack.us/img175/5717/60413547vb3.th.jpg [Broken]

Can someone please explain why the potential does not equal zero at the neutral point - wouldnt the two potentials cancel each other out?

Thanks

Hi nokia8650! Where is the potential being measured from (in other words, where is zero potential)?

Potential is often measured "from infinity" …

in that case, the potential will only be zero at an infinite distance from both the Earth and the Moon. Last edited by a moderator: