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Momentum09

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## Homework Statement

Given: The universal gravitational constant G = 6.67 E-11, the mass of the earth M = 5.98E24, and its radius R = 6.7 E6. How much work must an external force do on the satellite to move it from a circular orbit of radius 2R to 3R, if its mass is 2000kg? Answer in Joules.

## Homework Equations

I know that E = -GMm/2r, where M is the mass of the earth and m = satellite.

## The Attempt at a Solution

So I calculated the total energy in each radii,

for 2R, -GMm/4R

for 3R, -GMm/6R

then I subtract one from the other to get the net energy change. I don't know what to do after that. Please help. Thank you!