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Homework Help: Solving a Term about gravitation to r

  1. Mar 4, 2016 #1
    1. The problem statement, all variables and given/known data
    I want to know how this equation is getting solved to r. I know the result, but I want to know how :)

    2. Relevant equations
    γ*m*Me/r = 4Π2*m*r/T^2

    Solution does need to be: r = ^3√γMeT^2/4Π^2 (^3√ should mean the 3rd root/radical)
    3. The attempt at a solution
    I am so far:
    γ*m*Me/r^2 = 4Π2*m*r/T^2 ( shortening the terms now)
    γ*Me/r = 4Π2/T^2
    γ*Me*/T^2/r*Π2 = 0

    Now I do not know how to continue, I am 99% sure that I have done something wrong.
    Greetings from Germany! :)

    Here is a picture about the term: http://[url=http://postimg.org/image/war0n6zxf/][ATTACH=full]200042[/ATTACH] [ATTACH=full]200043[/ATTACH]
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Mar 4, 2016 #2


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    Staff Emeritus
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    Homework Helper

    The equation above seems to be the one taken from your text.
    You cancelled the variable r incorrectly. You should have multiplied both sides of the original equation by r2.

    After that, leave r3 one one side of the equation and move everything else to the other side. Solve for r.

    This is just simple algebraic manipulation.
  4. Mar 5, 2016 #3
    I understood it now. Thanks for the help! :smile:
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