okay, i have a question about physics.
the gravitational field strength at the surface of the Earth is 9.8 N/kg right where the radius from the earth's centre = 1 right?
So if you were trying to find the gravitational field strength at a certain radius from the earth's centre you would divide 9.8N/kg by the square of that radius right?

For example, if you were two radii from the Earth's centre, then the gravitational field strength would be 9.8N/kg divided by (2)^2, right?
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You can certainly work out how far objects are apart from their masses and the gravity between them. There were a few questions of this type in my first year exams. The law in question is Newton's law of gravitation.
Gravity at a certain radius is given by

a = (MG)/r^2

M = mass of big object (earth)
G = Gravitational constant, NOT g, 6.67 x 10^-11, I can't remember, look it up
a = Acceleration due to gravity.

I'd normally explain it in depth, but I'm tired, so if you need any help, PM me, and I'll be happy to explain in depth in a day or so.

EDIT:

Yes, you're absolutely right, it's an inverse square law. Sorry, half asleep.
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Last edited by LordBishek at Sep 21, 2008,
the radius from the earths core, for all intents and purposes, is generally a constant, as regardless of how far you dig in, you are still pretty much the same distance as you were before.

(that is a direct quote from my physics professor)
I'm pretty sure mass is the only variable. or acceleration or something like that.
Last edited by tona_107 at Sep 21, 2008,
Quote by tona_107
the radius from the earths core, for all intents and purposes, is generally a constant, as regardless of how far you dig in, you are still pretty much the same distance as you were before.

(that is a direct quote from my physics professor)
I'm pretty sure mass is the only variable.

Yeah, but I think he's talking about much larger differences - two radii or more.
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Though our skin may not touch skin
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Yeah, but I think he's talking about much larger differences - two radii or more.

Oooh sorry bud, I guess I didn't really read it right.
Okay thanks, because i had a bunch of questions about this kind of stuff and i tried using the equation g = G(m/r^2) but it didn't work cuz i realized if G = 6.67 x 10^-1 etc etc then i would need the actual distance, not just the radii. Thanks for clearing things up for me guys
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Okay thanks, because i had a bunch of questions about this kind of stuff and i tried using the equation g = G(m/r^2) but it didn't work cuz i realized if G = 6.67 x 10^-1 etc etc then i would need the actual distance, not just the radii. Thanks for clearing things up for me guys

No worries man. GM is also called the gravitational parameter, and it's used a lot in these kind of calcs, so use this, it might help:

http://en.wikipedia.org/wiki/Standard_gravitational_parameter

May be worth learning a couple of the ones that crop uo in exams like Earth's, Jupiter's and the Sun's.
Oh my love, though our bodies may be parted,
Though our skin may not touch skin
Look for me with the sun-bright swallow,
I will come on the breath of the wind

I'M UNCONDITIONALLY HERS