# Satelites at different levels

1. Jun 2, 2007

### Langbein

Some satelites is just hanging there in a geostationary position, like TV satelites, communication satelites etc.

Some other satelites are moving around the earth with a time for rotating around the earth like something like 2-3 hours (??!!)

How can this be, some of then is just hanging, some are moving around with great speed. How can this be ?

Is the explanation as simle that they are doing their journey on different altitudes so that thy will have different tangential speed ?

Could it be that those that are moving around the earth at high speed balance out a higner gravitational force using the higher speed, while those that has geostationary levels are moving more slowly due to a smaller gravitational force ?

Is it like that and will it then be like that all geostationary satelites have to be located on the same level to balance out the gravitational force using the sentripetal accelleration ?

Faster satelites should then be on a lower level right ?

What would then be the (sipmplified) equataion for the speed of a satelite on a established level ?

Is it true that all geostationary satelites are on the same level ?

2. Jun 2, 2007

3. Jun 2, 2007

### Janus

Staff Emeritus
yes
yes
right
$$v = \sqrt{\frac{GM}{r}}$$
Where:
G is the universal gravitational constant
M is the mass of the planet the satellite is orbiting
r is the radius of the orbit as measured from the center of the planet.
For the Earth, GM is equal to ~4 x 1014
Yes, and they (as opposed to geosynchronous satellites) also all orbit in the plane of the equator. This is known as the Clarke Belt. (Named after the person who, in 1947, first suggested that you could put a satellite there and use it to relay signals around the world.)

Last edited: Jun 2, 2007
4. Jun 2, 2007

### Langbein

Thanks a lot for two really good answers ! :-)

.. I only has some small problems with the formula in the last answer ..
(But I try to find it out ..)

5. Jun 2, 2007

### Janus

Staff Emeritus
Sorry, I fixed the formating. try it now.

6. Jun 2, 2007

### Langbein

Thanks a lot, It works fine now :-)