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Homework Help: Electrostatic forces/fields

  1. Oct 31, 2011 #1
    1. The problem statement, all variables and given/known data

    An unknown charge and a charge of 60 nC are 2.0m apart. The electric field strength is zero at a point 0.80m from the unknown charge on a line connecting the two charges. Find the magnitutde of the unknown charge.

    2. Relevant equations

    Coulomb constant: 8.99 x10^9

    3. The attempt at a solution
    I tried making an equation with the info given, but it doesn't seem like it's gonna help me:

    i think i just need a push in the right direction
  2. jcsd
  3. Nov 1, 2011 #2
  4. Nov 1, 2011 #3
    What is the equation of an electric field with 2 charges present?
  5. Nov 1, 2011 #4
  6. Nov 1, 2011 #5
    If the system has 2 charges how do you find the force on a third charge at a point? :)
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