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Homework Help: Formula help

  1. Nov 16, 2004 #1
    Here is the ex. in the book. Two 3.kg textbooks are .15 apart. What is the gravitational attraction?
    The answer is given 2.7*10-8
    I also know the formula is F=Gm1m2/r
    I just do not understand what they are doing to get the answer.

    (6.67*10-11 N-m2kg2)(3.kg)(3.kg)/.15
    This is the formula I am trying to use

    Please help!
  2. jcsd
  3. Nov 16, 2004 #2


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    distance squared.
  4. Nov 16, 2004 #3
    I know the formula I do not understand how to solve it
  5. Nov 16, 2004 #4

    Tom Mattson

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    Look closer. Your formula is wrong, and Nate's is right (note the "r2" in the denominator).
  6. Nov 18, 2004 #5

    What I do not understand is what to do with the formula. How do you solve this problem? THis is just an example in the book with the answer given but I do not understand what to do with the formula to solve it. Sorry
  7. Nov 18, 2004 #6


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    Plug in the numbers:
    [tex]F=\frac{m_1m_2G}{r^2} \Rightarrow \frac{3 \times 3 \times (6.67 \times 10^{-11})}{0.15^2}[/tex]
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