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Homework Help: Electrostatic/gravitational force q

  1. Jan 29, 2007 #1
    1. The problem statement, all variables and given/known data
    Determine the ratio of the electrostatic to the gravitational force between an electron and a proton

    2. Relevant equations
    I wasn't too sure where to start with this so i used the following equations:
    Electrostatic force f = (charge on proton*charge on e-)/(4*pi*epsilon*d^2)

    and gravitational force p = G*m1*m2/(4*pi*d^2)

    epsilon = 8.854187*10^-12
    charge on Proton = +1 C
    charge on electron = 1.6*10^-19
    G = 6.67*10^-11
    mass of proton = 1.6726231*10^-27
    mass of e- = 9.109*10^-31

    3. The attempt at a solution
    then i said f/p = (1.6*10^-19)(1)/(4*pi*epsilon*d^2)/(6.67*10^-11)*(9.109*10^-31)(1.6726*10^-27)/(4*pi*d^2)

    f/p = 1.414459*10^58

    is this answer correct, i have a feeling im going wrong somewhere,either in my methodology or figures
    any help would be much appreciated
    thanks debs:biggrin:
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Jan 29, 2007 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    For your attempt at the solution I believe the 1 in brackets is supposed to be the charge of a proton. The charge of a proton is not 1 coulomb, it is exactly the same magnitude as the charge on an electron but with the opposite sign.
  4. Jan 30, 2007 #3
    thanks a million,wasn't too sure about that one but it obviously makes sense that way!
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