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Homework Help: Point charge - magnitude calculations

  1. Jan 18, 2010 #1
    1. The problem statement, all variables and given/known data
    A 4.9-µC point charge is located at x = 1.1 m, y = 3.1 m, and a -3.9-µC point charge is located at x = 2.1 m, y = -1.9 m.

    (a) Find the magnitude(inkN/C) and direction(in degrees) of the electric field at x = -3.2 m, y = 0.9 m.

    (b) Find the magnitude(in N) and direction(in degrees) of the force on a proton at x = -3.2 m, y = 0.9 m

    2. Relevant equations



    3. The attempt at a solution
    We haven't been taught this in class specifically, so i donn't know how to go about it. Help please!
     
  2. jcsd
  3. Jan 18, 2010 #2
    Use the equation for the Coloumb force:

    [tex]\vec{F}=k_e \frac{q_1q_2}{r^2} \hat{r}[/tex]

    And the electric field

    [tex]\vec{E}=\frac{\vec{F}}{q}=k_e\frac{q}{r^2}[/tex]

    and the superposition principle (E=E1+E2)
     
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