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Calculating electrostatic force on particles

  1. Jan 30, 2017 #1
    1. The problem statement, all variables and given/known data

    Phy 204.PNG
    2. Relevant equations
    F=(kq1q2)/d^2

    3. The attempt at a solution
    So it should be fairly easy to use "parts" to come up with each answer
    Part a
    Because particle 1 has no pull in the x direction I should be able to ignore it when finding the x component of the force
    Fx=k*q3*q4/a^2+k*q3*q2/(a*sqrt2)^2*cos45
    =7.46E-4 N
    This was incorrect and I did not attempt part 2 as I figured my mistake would carry over to that similar calculation
     
  2. jcsd
  3. Jan 30, 2017 #2

    BvU

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    Check your calculation. I get something else. Spell it out if you want it checked.
     
  4. Jan 30, 2017 #3
    8.99E9*(9.5E-8)*(-9.5E-8)/(2.03E-3)+8.99E9*(9.5E-8)(-5E.7)/(4.05E-3)cos45deg
    =-0.114623N
    it seems that I made a mistake on my cm to m conversion and if I remember correctly this should be absolute value of the charges so
    =0.114623N
     
  5. Jan 30, 2017 #4

    BvU

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    Numerical value same as what I found.

    No. You are asked for an x-component, which can be negative or positive. Make a sketch to find the right sign. What does the F in your relevant equation represent ?
     
  6. Jan 30, 2017 #5
    I realized this after I sent it. Both q2 and q4 are opposite charges of q3 so they are both attractive forces. In regards to the y component q1 will repel q3 while q2 will again be attractive and by glance you can tell the effect of q1 will be greater than q2 you can assume that the answer will be negative in the y direction
     
  7. Jan 30, 2017 #6

    BvU

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    Assuming is one thing, calculating is better :smile:.
     
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