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Homework Help: Gravitational Force between two equal masses

  1. Nov 14, 2011 #1
    1. The problem statement, all variables and given/known data

    Two equal masses are precisely 1 m apart from each other. The gravitational force each exerts on the other is exactly 2. What is the value of each mass?

    *a. 1.73*10^5kg

    b. 1.50*10^10kg

    c. 2.50*10^5kg

    d. 1.58*10^10kg

    2. Relevant equations

    F=Gmm/r^2

    3. The attempt at a solution

    I did
    F=Gmm/r^2
    2=G2m/1 (because the masses are equal)
    m=2*1/2G
    m=1/G
    m=1.50*10^10kg

    I dont know why B is wrong and A is right (according to the answer key);
     
  2. jcsd
  3. Nov 14, 2011 #2

    I like Serena

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    Homework Helper

    Hi physgrl! :smile:

    I'm afraid that [itex]m \cdot m \ne 2m[/itex].
     
  4. Nov 14, 2011 #3
    uups my mistake :s
     
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