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Homework Help: Coulomb’s Law

  1. Feb 4, 2005 #1
    Two small nonconducting spheres have a total charge of 80 microC. When place 1.06 m apart, the force exerts on the other is 12 N and is repulsive. What is the charge of each. What if the force were attractive?

    Given: k, F = 12 N if repulsive but F = -12 N if attractive, Q1 + Q2 = 8 x 10^-5 C, r = 1.06 m

    Using Coulomb’s Law, isolate Q1Q2 .

    Q1Q2 = 1.498 x 10^-9 C?

    Then I thought I would use substitution for Q1 + Q2 = 8 x 10^-5 C and Q1Q2 = 1.498 x 10^-9 C.

    But now I get a huge quadratic equation. Is this the correct method??

    Last edited: Feb 4, 2005
  2. jcsd
  3. Feb 4, 2005 #2


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    Staff Emeritus
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    Your method is correct. You have to solve the qudratic to find Q1, Q2. There really isn't a better way.
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