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Homework Help: Coulomb's law

  1. Mar 31, 2012 #1
    1. The problem statement, all variables and given/known data

    see attachment

    2. Relevant equations

    3. The attempt at a solution

    Do you see the step where they go from (1.35keq2)/a2

    to 1.91keq2)/a2 ?

    I can't get that step. To my mind. If you square 1.35 then take its square root, you get 1.35 not 1.91

    Attached Files:

  2. jcsd
  3. Mar 31, 2012 #2
    [tex]\sqrt{1.35^2 \left (\frac{k_e q^2}{a^2} \right )^2 +1.35^2 \left (\frac{k_e q^2}{a^2} \right )^2}[/tex]
    [tex]\sqrt{\left (\frac{k_e q^2}{a^2} \right )^2(1.35^2 +1.35^2) }[/tex]
    [tex]\frac{k_e q^2}{a^2}\sqrt{1.35^2 +1.35^2 }[/tex]
    [tex]\frac{k_e q^2}{a^2}\sqrt{(2)(1.35^2)}[/tex]
    [tex]\frac{k_e q^2}{a^2}\sqrt{2}1.35[/tex]
    [tex]\frac{k_e q^2}{a^2}1.91[/tex]
  4. Mar 31, 2012 #3


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    If you square 1.35 then multiply by 2, then take the square root of that result you do get 1.91, approximately.
  5. Mar 31, 2012 #4

    Excellent answer. If only more math texts included as many steps as you do!!! I really appreciate it.
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