1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: 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!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook