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Gravitational Acceleration-Orbital Motion

  1. Nov 10, 2011 #1
    1. The problem statement, all variables and given/known data

    The weight of a 0.60 kg object at the surface of Planet V is 20 N. The radius of the planet is 4 x 10^6 m. Find the gravitational acceleration at a distance of 2 x 10^6 m from the surface of this planet.

    a. 8.9 m/s2
    b. 11 m/s2
    c. 13 m/s2
    d. 18 m/s2


    2. Relevant equations

    F=ma
    a=MG/r^2


    3. The attempt at a solution

    I did
    acceleration at surface=20N/.6kg=33.33m/s^2
    acceleration at surface=MG/r^2
    MG=33.33m/s^2*(4x10^6)^2

    acceleration at a distance=MG/(r+d)^2
    a at a distance=(33.33m/s^2*(4x10^6)^2)/(2x10^6+4x10^6)^2
    a=14.8m/s^2 which is not in the options
     
  2. jcsd
  3. Nov 10, 2011 #2
    I can't see anything wrong with your method. I did exactly the same and got the same answer as you !!!!
    It will be interesting to see if there are any other responses to your posting.
     
  4. Nov 10, 2011 #3

    phyzguy

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    Science Advisor

    I think you did it right and the question is wrong. Anyone else see an error?
     
  5. Nov 10, 2011 #4
    I get 8.89...
     
  6. Nov 10, 2011 #5
    The weight will be 8.89N
     
  7. Nov 10, 2011 #6
    Settled! Answers wrong
     
  8. Nov 10, 2011 #7

    phyzguy

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    Science Advisor

    It doesn't ask for the weight, it asks for the acceleration, which should be 14.8 like the OP calculated.
     
  9. Nov 10, 2011 #8
    thanks :D
     
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