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Finding altitude of a satellite if you know it's radius and mass

  1. Sep 23, 2013 #1
    1. The problem statement, all variables and given/known data

    A 135 kg satellite experiences a gravitational force by the Earth of 960 N. What is the radius of the satellite's orbit. And altitude? I already found the radius and I came up with 7489.99 km. I just need help finding the altitude.

    2. Relevant equations

    Equation for period: T= 2∏ times the square root of (r^3) / (GMe)
    Period= how long it takes to go around once.
    From this step what do I do next?

    3. The attempt at a solution

    For T I did 2∏ times the square root of (4.2E11) / (3.99E14)

    I got 4.2E11 but taking the radius I got up above (7489.99) and then curbing it. I got 3.99E14 by taking G (6.67E-11) times Me (5.98E24).
     
  2. jcsd
  3. Sep 23, 2013 #2

    SteamKing

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    What is the definition of altitude?

    If you know the radius of the orbit about the earth, what other number do you need to know to calculate altitude?
     
  4. Sep 23, 2013 #3
    Altitude=the height of an object. I also need to know the speed of the orbit?
     
  5. Sep 23, 2013 #4

    D H

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    You do not need to know the object's orbital velocity.

    Altitude is the height of the object above what?
     
  6. Sep 23, 2013 #5
    I need to know the objects radius?
     
  7. Sep 23, 2013 #6

    D H

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    No. You are missing something very basic. What is the satellite orbiting?
     
  8. Sep 23, 2013 #7

    SteamKing

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    Height of an object relative to what? The center of the earth? The upper shelf in your closet? The top of the Empire State Building?
     
  9. Sep 23, 2013 #8
    The satellite is Orbiting earth...
     
  10. Sep 23, 2013 #9

    D H

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    You already know the distance from the center of the Earth to the satellite. So how far is the satellite above the surface of the Earth?
     
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