# Satellite pedigree/apogee ratio. 2 values given both __Earth radii

1. Jun 27, 2010

### bharminder

A satellite is placed in a noncircular orbit about the Earth. The farthest point of its orbit (apogee) is 3.6 Earth radii from the center of the Earth, while its nearest point (perigee) is 2.7 Earth radii from the Earth's center. If we define the gravitational potential energy U to be zero for an infinite separation of Earth and satellite, find the ratio

Upedigree
Uapogee
.

I tried 3.6 Earth radii / 2.7 Earth radii and put 1.3 as the ratio. Then i tried the other way around with 2.7 / 3.6. I looked in my textbook and there is no explanation for this type of problem. I know the equation for gravitational potential energy ( U = (G m1 m2) / r

but I don't have either mass.

Bobby

2. Jun 28, 2010

### Filip Larsen

Try write up the division anyway using the unknown masses and see what happens.

And please make your spell checker stop replacing perigee with pedigree :)

3. Jun 28, 2010

### astrozilla

The other way round

but this is not even a level question