1. orbits...
Gidday again...
I've been trying to make a moon orbit around a planet for about 4 days
now, but to no avail. I've been to as many physics sites as the search
engines find, but can't find anything of use.
Anyone know of some formulae?
The formula's I have find:
distance between moon and planet
gravitational force on moon at x distance from planet
now, how the hell can I get the #*%^@$ moon to rotate around the
planet?? :)
Thanks,
Mike :)
==
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Mike Fowler - wildcat_nz at yahoo.com
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2. Re: orbits...
The radial distance of a body to another can be given by:
(x+a)^2 + (y+b)^2 = r^2
where x is the independent variable, y is the dependent, r is the radius
from the center of the "circle" and a and b are the center (location) of
the body around which you are rotating.
solve for y.
increment x and watch it go!
snortboy
3. Re: orbits...
On Fri, 25 Sep 1998, Noah Smith wrote:
> The radial distance of a body to another can be given by:
>
> (x+a)^2 + (y+b)^2 = r^2
[snip]
> solve for y.
>
> increment x and watch it go!
y = sqrt(r*r - power(x+a, 2)) - b ?
what if (x + a) > r? /me rubs head.
--
Carl R White
E-mail...: cyrek- at -bigfoot.com -- Remove the hyphens before mailing. Ta :)
Url......: http://www.bigfoot.com/~cyrek/
"Ykk rnyllaqur rgiokc cea nyemdok ymc giququezka caysgr." - B.Q.Vgesa
4. Re: orbits...
first, i made an error in my formula, it should be:
(x-a)^2 + (y-b)^2 = r^2
Carl R. White wrote:
> y = sqrt(r*r - power(x+a, 2)) - b ?
>
> what if (x + a) > r? /me rubs head.
alright, here goes. the above function describes a series of points using
pythagoras' theorem, where x-a and y-b are the length of the legs and r is the
length of the hypotenuse. I haven't actually tested it numerically, but it
would seem that the length of r (and therefore r*r) would always be greater
than the length of a leg (x-a, or (x-a)^2).
I think. I don't remember fer sure...it's been awhile.
snortboy
5. Re: orbits...
- Posted by DHarte at AOL.COM
Sep 25, 1998
-
Last edited Sep 26, 1998
I assume that you want to know how to simulate an orbit using real physics.
To get one body to orbit another, you must give it an initial velocity. If you
want to make it move in a circle, give it initial velocity, v0=sqrt(GM/r),
where M is the mass of the planet, r is the radial distance (between the
centers of mass), and G is the gravitational constant. This velocity must be
tangent to the circle that you want the object to orbit at.
To get the rest of the simulation, you use Fn=GMm/r^2, an=Fn/m, vn=v(n-1)+an
dt, xn=x(n-1)+vn dt (the n's and (n-1)'s are supposed to be subscripts). These
are vector equations. You will probably have to parametrize the variables (or
use sequences for vectors) to get it to work.
Abraham Harte
6. Re: orbits...
---Noah Smith wrote:
> The radial distance of a body to another can be given by:
>
> (x+a)^2 + (y+b)^2 = r^2
>
cheers... that should do the trick...
Thanks again
Mike :)
==
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Mike Fowler - wildcat_nz at yahoo.com
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