Kepler's Laws problems

  1. 1) Satellite X and Satellite Y orbit the earth. The distance between X and the earth is 8 times greater than the distance between Y and the earth. Using Kepler's Laws, the period of satellite X is what factor times the period of satellite Y?

    R is the distance between satellite Y and the earth

    I used Kepler's third law:

    T^2=R^3 for Y
    T^2=(8R)^3 for X

    So T for Y would be R^(3/2)
    and T for X would be 22.6*R^(3/2)

    So the factor is 22.6 right? But the answer key says "4.0" So am I right?

    2) There is a point between the earth and the moon where the net force of gravity on an object located at that point would be zero. I have no idea which formula to use on this problem, please help.
  2. jcsd
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