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The following question is giving my friend and I a really hard time. My work is shown below.

'what is the total amount of energy needed to place a 2.0 x 10^3 kg satellite in circular Earth orbit, at an altitude of 5.0 x 10^2km above the surface of the earth?

Here are all the numbers needed to carry out the problem:

M = 5.8 x 10^24 kg (mass of earth)

m = 5.0 x 10 3 kg (mass of satellite)

r1 = 6.38 x 10^6 m (radius of earth)

r2 = 5.0 x 10^5 m + 6.38 x 10^6 m (altitude plus radius of earth)

G = 6.67 x 10^-11 N/kg. (Earth's gravitational field strength)

I figured that the energy needed would be equal to the energy of the satellite in orbit minus the energy of the satellite on earth's surface....giving thus:

E(needed) = -1/2(GMm/r2) - (-GMm/r1)

where did I go wrong?

Thx!

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# Satellite Energy Problem HELP!

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