gravity

[CPL.Luke]

is there a gauss's law for gravity?

 

I mean that as an equivalent law that deals with gravity

[ydoaPs]

what is gauss's law? is it about magnetism?

[CPL.Luke]

closed surface integral of E differential a =charge encompassed / epsilon not

 

(leaving it to someone who can do latex to re-write that)

 

it has to do with electromagnetism in its native form it is the basic natural law that governs electrostatics. It can be redone for magnetism but its equal to zero (just tells you that there is no basic charge of magnetism.

 

it can also be re-written to

 

epsilon not (flux e)= q encompassed

[ydoaPs]

[math]\LaTeX[/math] isn't working right now anyway.

[CPL.Luke]

http://en.wikipedia.org/wiki/Gauss%27s_law

[Meir Achuz]

Newton's gravitational law and Coulomb's law have the same form ~1/r^2.

Therefore Gauss's for the E field translates directly into a Gauss's law for the gravitational force field. Poor Newton predated Gauss by over a hundred years, so he had to work harder without G's law.

[Johnny5]

is there a gauss's law for gravity?

 

I mean that as an equivalent law that deals with gravity

 

Classical electrodynamics is an example of a field theory, and gravity can also be formulated as a field theory. Gauss' law is a consequence of the mathematics of a field theory, in general it stems from the mathematical nature of an inverse square law, as Meir pointed out.

 

So the answer is yes.

 

Regards

[CPL.Luke]

does anybody know what it is?

 

or how to derive it?

 

or where to start?

 

and would this be right

 

closed surface integral of (g da) =m encompassed

 

 

the trick would be to know what constant to put under m

 

 

my guess for that would be 1/(G4pi)=C

 

as that would create a constant that could be plugged back in and get the law of universal gravitation

 

so the final equation would be closed surface integral of (g da) =mass enc/ C

[Johnny5]

When the latex is working again, I'll show you what to do.

[swansont]

Oh, come on people. Type the derivation in (and wait for that to happen)? This sort of thing is what the internet is all about. Google on it and get some links. Other people have already done the work.

 

Gauss's Law derivation

 

For gravity, replace the analogous terms.

[CPL.Luke]

but just out of curiosity are the two fields directly analougous? as gravity does not have a sign

[swansont]

but just out of curiosity are the two fields directly analougous? as gravity does not have a sign

 

Sure it does - it's positive. Mathematically they are analogous, at least using Newton's law. Having opposite charges only changes the direction of the field vector, but the surface integral doesn't care about that.

[ydoaPs]

total guess here, but is it [math]\oint_A{g}\cdot{dA}=\frac{m}{\epsilon_0}[/math]?

[swansont]

total guess here, but is it [math]\oint_A{g}\cdot{dA}=\frac{m}{\epsilon_0}[/math']?

 

No, you'd replace the 1/4[math]\pi \epsilon_0[/math] with G.

[ydoaPs]

my buddy over at physicsforums said it is [math] \oint_A \mathbf{E} \cdot d\mathbf{A} = 4 \pi G M [/math]

[swansont]

my buddy over at physicsforums said it is [math'] \oint_A \mathbf{E} \cdot d\mathbf{A} = 4 \pi G M [/math]

 

Yep. That's what you get (on the right-hand side) if you do what I said.