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Calculate mass of oil droplet between parallel plates

  1. Mar 3, 2015 #1
    1. The problem statement, all variables and given/known data

    1. A droplet of oil, carrying an extra charge of one electron, is held motionless between parallel plates separated by 1.89 cm, with a potential difference of 39.8 kV. What is the mass of the droplet?

    2. Relevant equations

    E=0.5QV
    C=Q/V
    3. The attempt at a solution
    Really don't even know how to start here..I figured I would need kinetic energy to find the mass but the velocity is 0, so there would be none.
     
  2. jcsd
  3. Mar 3, 2015 #2

    Dick

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    Science Advisor
    Homework Helper

    The problem should really tell you this, but you should assume that the force holding the droplet fixed is the weight of the droplet. Find the electric force on the droplet and set it equal to the gravitational force.
     
  4. Mar 3, 2015 #3
    Oh, well that was easy then. Thanks!
     
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