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: Cant get y-component of point charges on test charge

  1. Oct 3, 2007 #1
    1. The problem statement, all variables and given/known data
    Six point charges, four positive (+q) and two negative (-q), are fixed at thepositions shown (i attached a .gif file --pls tell me if this isnt visable) in the x-y plane; q = 2.1 × 10-6C and a = 0.93 m. A test charge Q = 0.6 × 10-6C is at the origin.

    (a) Find the x- and y-components of the total force on Q:

    2. Relevant equations
    i successfully calcd the x-component (-.017016N) but cant get the y component

    3. The attempt at a solution

    heres what i did

    1. labelled the charges A thru F starting with the charge on the neg y-axis (A) and the labelled in cw direction.

    2. so for y component everything either cancels or has no y-component, EXCEPT for the 2 charges on the y-axis. These are both pos charges.
    so heres the calc
    Ay = (9*10^9)(2.1*10^-6)(.6*10-6) / (.93^2) = .01311N (pos charge)
    Dy = (9*10^9)(2.1*10^-6)(.6*10-6) / (.93^2) = .01311N (also pos charge)
    so 2(.01311) = .02622N
    this is wrong!
    please help!
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution

    Attached Files:

  2. jcsd
  3. Oct 3, 2007 #2


    User Avatar
    Homework Helper

    No. this is wrong. The two charges on the y-axis exert equal but opposite forces on Q, hence they cancel.

    Which are the two charges you need to consider?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook