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Electric Charge Question

  1. Jan 18, 2006 #1
    A small plastic ball of mass 6.10 10-3 kg and charge +0.150 µC is suspended from an insulating thread and hangs between the plates of a capacitor (see the drawing). The ball is in equilibrium, with the thread making an angle of 30.0° with respect to the vertical. The area of each plate is 0.0150 m2. What is the magnitude of the charge on each plate?
    I tried several times and the most reasonable answer I get is .9715 m but wrong... Thanks in advance
  2. jcsd
  3. Jan 18, 2006 #2


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    Staff: Mentor

    Please show your work.

    This is a statics problem. The electric force = Fe = qE must equal the restoring force for a net force of zero on the ball.

    Start by determing the restoring force on the ball, i.e. the gravitational force. Write out the force balance equation.
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