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Homework Help: Weight and Radius

  1. Apr 14, 2008 #1
    1. The problem statement, all variables and given/known data
    Pat's mass is 65.5 kg on Earth's surface. What would Pat's weight be at an altitude twice the radius of the Earth

    2. Relevant equations
    G = 6.67X 10^-11

    We are not given the numerical radius of the Earth

    3. The attempt at a solution
    I tried to manipulate the formula a bit:
    (using the gravitational law)
    Fg = (65.5)x/ 2^2

    And that got me nowhere.
    I also know the answer is 71.4N but how you get there is what I don't understand.
  2. jcsd
  3. Apr 14, 2008 #2


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    Homework Helper

    This equation should work. What are you using for each variable? Look up data you need. It's probably in your textbook somewhere.
  4. Apr 14, 2008 #3


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    Science Advisor

    While hage's solution is valid, I think we know g=9.8 for the surface of the Earth. Therefore, you can look at the equation and see how this force would change as R increases. Think about what is constant and what is changing.
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