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Electrostatic equilibrium, deflection of a cobweb

  1. Dec 10, 2014 #1
    1. The problem statement, all variables and given/known data

    9KbiO40.png
    2. Relevant equations

    After creating a FBD and analyzing the forces, I get the equation for the angle as

    ## tan \theta = \frac{k q^2}{m g r^2} ##

    3. The attempt at a solution

    I have tried to find a way to find the distance between the charges ## r ##, but the only way I can think of to find it required the angle. I do not know how the question can be solved without knowing at least one of the two variables, and my first inclination is just to assume there is not enough information.

    Any help would be appreciated! Thanks!
     
  2. jcsd
  3. Dec 10, 2014 #2

    CWatters

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    Science Advisor
    Homework Helper

    I think you can write another equation for r in terms of theta using the geometry alone..

    Hint: You are given the dimension 0.35m
     
  4. Dec 10, 2014 #3

    Doc Al

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    Staff: Mentor

    Find the relationship between r and ##\theta##.

    (CWatters beat me to it while I was snoozing!)
     
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