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Homework Help: Point Charges

  1. Nov 11, 2008 #1
    Two point-like objects carry charges of q1 = +4C and q2 = -3C and are separated by
    a fixed distance of 50 cm.

    (a) Determine the point (other than infinity) at which a point-like positive charge will
    experience zero net electrostatic force due to the two fixed charges.

    q1 = +4C .......................... q2 = -3C .................... +ve charge
    .. + <----------.5m----------> - <---------xm---------> +

    +ve charge has to be closer to the q2 charge but further away from q1. ( positive charge = 1.6*10^-19 C )

    So you need to balance forces?

    let q = positive charge
    Force q1 on q = -Force q2 on q
    (4C * q)/(.5 + x)^2 = -(-3C * q)/x^2

    Have I set this equation up properly?

    Any help greatly appreciated,

    EDIT: I figured out my problem. I wasn't using the quadratic formula properly to solve for x. So how do I delete a post?
    Last edited: Nov 11, 2008
  2. jcsd
  3. Nov 11, 2008 #2


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    Staff Emeritus
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    Gold Member

    Looks good to me :approve:
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