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Homework Help: Electricity Questions

  1. Jul 4, 2006 #1
    Two particles each have a mass of 5.3 10-3 kg. One has a charge of +5.0 10-6 C, and the other has a charge of -5.0 10-6 C. They are initially held at rest at a distance of 0.75 m apart. Both are then released and accelerate toward each other. How fast is each particle moving when the separation between them is one-half its initial value?

    ok, I know:
    q1 = +5.0 x 10^-6 C
    q2 = -5.0 x 10^-6 C
    r = 0.75m
    m = 5.3 x 10^-3 kg

    Since they are opposite charges they will atract eachother.

    I can't seem to figure out where to begin on what formula to use to discover the speed without any time.
  2. jcsd
  3. Jul 4, 2006 #2
    the fastest way would be transfering the potential energy difference to kinetic energy.

    [tex]\Delta U=\frac{mv^2}{2}+\frac{mv^2}{2}[/tex]

    if they didn't have the same mass you had to use the momentum conservation eq. aswell.
    Last edited: Jul 4, 2006
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