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# How to solve a physics question in involving satellites?

4. A 75 kg satellite is placed in orbit at a height of one earth radius above the earth's surface. That means that gravity is 25% weaker than at the surface.

b. Value of gravity in that orbit is 2.45 m/s/s.

c. Gravitational force acting on satellite is 180 N.

d. Centripetal force is the same as c.

e. The satellite's distance from the earth's centre is how much? I need to find the radius, and I have the mass, acceleration and centripedal force. I could use the equation ac = v2/r but I don't have the velocity. I've tried using other equations, but I need the period of orbit and there is no information about it!

### 2 Answers

- Anonymous10 years agoFavorite Answer
mv^2 / R = 180 = mg = m . 2.45

No way to the period or radius from here....

You have to assume G and M(e) ( 6.67 . 10^–11 and 5.98 . 10^24 )

and use GM(e) . m / R^2 = m . 2.45

That will give you the radius but is it the method wanted???

Source(s): Old teacher - ?Lv 44 years ago
you should combine all of those equations: stress as a results of gravity: F = GMm/R² ("R" is satellite tv for pc's distance from earth's midsection) Newton's 2d regulation: F = ma Acceleration of an merchandise in around action: a = v²/R So: F = ma substitute the gravity formula for "F" GMm/R² = ma Divide out the satellite tv for pc's mass "m": GM/R² = a substitute the around action formula for "a": GM/R² = v²/R next steps: * sparkling up algebraically for "v" * Plug in values for "G" and "M" (mass of earth). you will ought to look them up. * Plug in value for "R" (it extremely is the radius of the earth plus 2600 km. you will ought to look up the radius of the earth.)