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Homework Help: Electrostatic Net Force Problem

  1. Jan 8, 2012 #1
    1. The problem statement, all variables and given/known data
    I am trying to help a friends daughter understand her physics homework. We have been stumped for hours! We don't really understand what her teacher was talking about and what we have figured out has mostly come from google.

    The problem is (this is drawn out no real information is given): q2 1.0c directly north of that is q1 2.0c (the line between them shows a distance of 3m) then directly to the east of q2 is 4.0c and the distance between q2 and q3 is 4m. * (EDIT) Calculate net force on q2.

    2. Relevant equations


    3. The attempt at a solution
    Lots of google searches. The best we can come up with is that you plug in the information for each individual. (ie q1 q2, q1 q3, q2 q3), but if we did that there is nothing in her notes on how to combine them to come up with a net force? so for q1 q2 would be 3.06*10^9. Are we going about this all wrong? Any help would be appreciated.
    Last edited: Jan 8, 2012
  2. jcsd
  3. Jan 8, 2012 #2


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    Homework Helper

    Welcome to PF!
    The information you gave is clear, except there is no question. What are you trying to calculate? Net force on which charge?
  4. Jan 8, 2012 #3
    Sorry I edited. It says net force on q2.
  5. Jan 8, 2012 #4


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    Homework Helper

    Use the equation you wrote to find the force on q2 due to the charge q1.
    Then use it again to find the force due to the 4 C charge.
    Finally, add the two force vectors. You can do it by drawing arrows on graph paper, or sketching them on plain paper and finding the sum by trigonometry (law of sines and law of cosines) or by splitting the one at an angle into horizontal and vertical components.
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