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Homework Help: Coulomb's Law

  1. Jan 14, 2006 #1
    A particle of mass 63 g and charge 59 [tex]\mu C[/tex] is released from rest when it is 71 cm from a second particle of charge -27 [tex]\mu C[/tex]. Determine the magnitude of the initial acceleration of the 63 g particle. Answer in units of m/s^2.

    I used Coulomb's Law, F= [tex] 1/4\pi \epsilon_o * (5.9 x10^-6 * -2.7 x 10^-6) / .71^2 [/tex]
    I know that E_o = 8.85 x 10^-12.
    Solving this gave me .284.
    Then I set it equal to ma.
    63 a = .284
    Solving for a gave me .00451 m/s^2.
    Can someone tell me what I'm doing wrong?
  2. jcsd
  3. Jan 14, 2006 #2


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    Staff Emeritus
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    Make sure the units are correct. If the force is in N, which it appears to be, then the mass must be in kg (0.063 kg = 63 g).

    Perhaps it would be helpful to keep a chart of cgs and mks units available.
  4. Jan 14, 2006 #3
    so if the rest of my setup is right, I get .063a= .284.
    Solving for a gives me 4.51 m/s^2, which still isn't right.
    Am I doing something else wrong?
  5. Jan 14, 2006 #4


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    Homework Helper

    59 microCoulombs = 59.E-6 C , not 5.9E-6 C
    same for the 27 uC .
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