# Homework Help: Working out the geostationary orbit

1. Jul 17, 2008

I have been given that this planet has a diameter of 1600km with a uniform density of 52000 per cubic metre. And if its moon is in a geostationary orbit around the planet and assuming that the sidereal is exactly 24 hours. How far is the geostationary orbit above the surface of the planet. And i need the answer in km.

I'm stuck in getting the mass of the planet as so far i have

radius of the geostationary orbit = cubed root of (GMpT2p over 4 pi 2)

so therefore the radius = cubed root of (6.6742 x 10-11 x (mass of the planet which i do not know how to find out x 864002 all over 4 pi 2)

some help would be much appreciated

thanks

2. Jul 17, 2008

### tusenfem

I guess you would have to calculate the volume of the planet?
I guess you would then do something with the density (for which you lack a unit)?
Somehow, magically, this leads to the mass of the planet?

3. Jul 18, 2008

thanks well i've posted it there now and yeah sorry it was meant to be 5200kg per cubic metre i've changed it for the new post now

4. Jul 21, 2008

### stapel

Neopets "Lenny Conundrum" contest, Round 271 (closes 23 July)

The actual text of this week's Neopets "Lenny Conundrum" contest puzzle (Round 271) is as follows:

"Assume the world of Neopia is a spherical planet with a diameter of 1600 km with a uniform density of 5200 kilograms per cubic metre. If the moon of Kreludor is in a geostationary orbit around Neopia, and assuming a Neopian sidereal day is exactly 24 hours, how far is that geostationary orbit above the surface of Neopia?"

To get the prize-winning answer for the latest "Lenny Conundrum" contest, try following the instructions here:

. . . . .Lenny Conundrum Solutions Blog

Another resource might be http://www.able2know.org/forums/viewtopic.php?t=42093 [Broken].

Eliz.

Last edited by a moderator: May 3, 2017
5. Jul 21, 2008

### cristo

Staff Emeritus
This is a homework help forum, designed to help students with their homework/classwork problems, not to answer quiz, or contest problems. Thus, I am closing this thread now.