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# Need to find the altitude of a satellite above the surface of the earth!?

I know the equation for for Force of gravity is (Gm1m2)/r2and that the equation for acceleration of gravity is GM/r2...

But my problem doesn't seem to supply enough information! Would you please help me?

Given: G=6.67259 * 10 ` ~11 (Ten to the negative 11 power)

Question:

A satallite moves in a circular orbit around earth at a speed of 2100 m/s. Find the satellite's altitude above the surface of the earth. Answer in units of m.

Is there an equation that I'm missing? To calculate acceleration using velocity you need time and radius. I don't have either!

Please help me!

Thank you so much,

Erica

### 2 Answers

- kirchweyLv 71 decade agoFavorite Answer
In a circular orbit, centripetal acceleration Ac = grav. acceleration Ag (that's why the orbit is circular, not an inward or outward spiral), thus

Ac = v^2/r = Ag = GM/r^2 ==> r = GM/v^2

Look up earth mass M, and solve for r. Then subtract earth radius re to find altitude h.

Using M = 5.9742E24 kg and re = 6378100 m, I get

h = 84015068 m.

- larameeLv 43 years ago
How To Find A Satellite

Source(s): https://shrinkurl.im/a0ebP- Login to reply the answers

Thanks. Worked well.