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Finding the x-component of a force using Coulomb's Law

  1. Apr 6, 2012 #1
    1. The problem statement, all variables and given/known data
    (1) A point charge q1 = -2.9 μC is located at the origin of a co-ordinate system. Another point charge q2 = 5 μC is located along the x-axis at a distance x2 = 8.6 cm from q1.

    The answer to this was -17.64N.

    (2) Charge q2 is now displaced a distance y2 = 2.4 cm in the positive y-direction. What is the new value for the x-component of the force that q1 exerts on q2?

    2. Relevant equations
    Coulomb's Law: F = k (q1q2)/(r^2)


    3. The attempt at a solution
    Seeing that q2's position had changed, I calculated the new force exerted using Coulomb's Law. I used 9*10^9 for k, and using the Pythagorean theorem, I calculated the new distance between the charges, which I got to be 0.089. After using Coulomb's Law, I got an answer of -16.37N. To find the x-component, I multiplied this value by cos(45), giving me a final answer of -11.58. This, however, is apparently incorrect and I'm confused as to why.

    Any help would be appreciated!
     
  2. jcsd
  3. Apr 6, 2012 #2
    Why did you chose 45 degrees as the angle?
     
  4. Apr 7, 2012 #3
    Ah, I see what I did wrong. I just assumed that because they had drawn the line they way they did in the figure, the angle was 45 degrees. Silly mistake, thanks for that!
     
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