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!

Electric force problem

  1. Feb 12, 2010 #1
    1. The problem statement, all variables and given/known data
    Hello forums! I'd like to ask you for your assistance on this particular problem:

    Three charges are placed at the edges of a triangle (Q1=+2 C, Q2=-4 C, Q3=+3 C) as shown on the picture (b=10 cm). What is the resultant force on charge Q2 (neglecting gravity and assuming the charges are in a vacuum)?

    TriangleZZZ.jpg
    2. Relevant equations

    F=k*Q1*Q2/r^2

    k=9*10^9 N m^2 C^-2

    3. The attempt at a solution
    The distance "a" is given by:
    tan 30°=a/b
    Which gives: a=5.7735 cm.

    Using the Pythagorean theorem I got: c=11.547 cm.

    Then I calculated the force between Q1 and Q2 to be: F1=-2.16*10^13 N
    Then I calculated the force between Q3 and Q2 and got: F2=-8.1*10^12 N

    The problem I'm having is calculating the resultant force (Fr) on Q2. Which sort of formula should I use to calculate it?
    I made a force diagram as well:
    Triangle2-1.jpg
     
  2. jcsd
  3. Feb 12, 2010 #2
    Force is a vector so you need to add the components. Find F2y and add it to F1 and then find F2x.
     
  4. Feb 12, 2010 #3
    I think I got it. So, what I did was this:
    sin 30°=Fy1/F2
    From this, I got: Fy1=-4.05*10^12 N
    then I added this to F1 and got: Fy2=Fy1+F1 => Fy2=-2.565*10^13 N
    I got the x component from:
    cos 30°=Fx/F2
    And got: Fx=-7.0148*10^12 N
    Then I used the Pythagorean theorem to find the resultant and got: Fr=[tex]\sqrt{(Fy2)^2+(Fx)^2}[/tex]
    Fr=-2.65919*10^13 N

    Does this look correct?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Electric force problem
  1. Electric force problem (Replies: 1)

Loading...