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calculating the distance of equal an opposite gravitational pull between the moon and earth
This problem has been annoying me for ages and I still haven't been
able to work it out. I am using the formula for universal garvitaional force and I know it is a simultaneous equation but I can't get it to work. Can anyone help. |
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calculating the distance of equal an opposite gravitational pullbetween the moon and earth
Jason wrote:
This problem has been annoying me for ages and I still haven't been able to work it out. I am using the formula for universal garvitaional force and I know it is a simultaneous equation but I can't get it to work. Can anyone help. I know diddly about math, but I can tell you that there is a point where the two gravitational pulls /plus the centrifugal force of the circular path/ (an important consideration) balance out. It's called L-1 and is stationary wrt Earth and moon. If this isn't something you already know about, plug "Lagrange Points" into a search engine. -- Regards, Mike Combs ---------------------------------------------------------------------- We should ask, critically and with appeal to the numbers, whether the best site for a growing advancing industrial society is Earth, the Moon, Mars, some other planet, or somewhere else entirely. Surprisingly, the answer will be inescapable - the best site is "somewhere else entirely." Gerard O'Neill - "The High Frontier" |
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calculating the distance of equal an opposite gravitational pull between the moon and earth
JRS: In article , seen
in news:sci.space.tech, Jason posted at Fri, 10 Oct 2003 19:35:52 :- This problem has been annoying me for ages and I still haven't been able to work it out. I am using the formula for universal garvitaional force and I know it is a simultaneous equation but I can't get it to work. Can anyone help. It need not be a simultaneous equation. Let the Earth's mass be M, the moon's m, the separation R, and the distance of the balance point from the moon be r. Field balance is when Gm/r^2 = GM/(R-r)^2, i.e. Gm(R-r)^2 = GMr^2. That is a simple quadratic. Since M/m ~ 81, to a first approximation one can ignore r in (R-r) and get r = R/9. If you want the Lagrange point L1, then the effects of rotation must be included; see URL:http://www.merlyn.demon.co.uk/gravity3.htm#L15. -- © John Stockton, Surrey, UK. Turnpike v4.00 MIME. © Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links; some Astro stuff via astro.htm, gravity0.htm; quotes.htm; pascal.htm; &c, &c. No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News. |
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