# Change in energy in orbiting satellite.

1. Apr 25, 2014

### Gianf

1. The problem statement, all variables and given/known data
A satellite of mass 45.5 kg orbiting the earth moves from an orbit of 7271 km to an orbit of 7356 km.
what is the work done by all forces acting on it?

2. Relevant equations
U=GMm/r

3. The attempt at a solution
I calculated the total energies of the satellite in both orbits which is -1/2GMm/r
This gave -1.2458Gj for the lower orbit and -1.2315 for the higher one.
Should the difference be the total work done?

2. Apr 26, 2014

### rude man

It says find the work done by all the forces acting on it.

Contemplate the possibility that this is a 'trick' question.

3. Apr 26, 2014

### Gianf

what would the trick be?

4. Apr 26, 2014

### rude man

Sorry, I think I misread the question. Actually, it's a bit misty. My reading of it now is that there was a circular orbit of 7272 km which gets moved to a NEW circular orbit of 7356 km.

Just use conservation of energy but remember to include potential and kinetic energies.