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Homework Help: Slopes of a Force vs. Charge and Force vs. Distance Graph

  1. Apr 15, 2008 #1
    1. The problem statement, all variables and given/known data
    We did a lab using two balls (one with a neutral charge and one with a negative charge). The independent variables were distance between the two balls and charge, while the dependent variable was force. We were to hang the neutral ball so that the negatively charged ball could affect the distance. We moved the negatively charged ball closer to the neutrally charged one, and usually a repulsion occurred. We found that the force vs. distance graph was directly proportional and the force vs. charge graph was inversely proportional. What do the slopes of each graph represent?

    2. Relevant equations
    Force/Distance = ?
    Force/Charge = ?

    3. The attempt at a solution
    Force's units divided by distance's units = N/m.
    Then for the charge graph, I'm not sure what the units of charge even are.
  2. jcsd
  3. Apr 15, 2008 #2


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    Homework Helper

    For the one with Force vs charge. The units are N/C... Recall what the force exerted per coulomb of unit +ve charge placed at a point represents..

    But what it seems that you were doing was testing Coulomb's law of

    [tex]F=\frac{Q_1Q_2}{4\pi \epsilon_0 r^2}[/tex]
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