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Homework Help: Electric Force Question and Spheres

  1. Jul 9, 2006 #1
    Three identically charged spheres A, B, and C, each with a charge of +3.0 * 10-7 C, are located at the corners of a triangle whose sides are 30 cm long and all the angles are 60 deg. What is the net force acting on sphere A?

    I figured the X coordinates cancel each other out. For the Y:

    kqAqB/r^2 cos 30 + kqAqC/r^2 cos 30

    since all charges and sides are equal:
    2(kq^2/r^2) cos 30

    the answer I get is 1.56 *10^-2 but the website says that is not correct. Does anyone know what I am doing wrong??
  2. jcsd
  3. Jul 9, 2006 #2

    Andrew Mason

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    Perhaps it is a problem with significant figures. Try 1.6 x 10^-2. Your method is correct.

  4. Jul 9, 2006 #3


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    I concur with Andrew. Since they gave the charge and length with two sig figs, they probably want you to give 1.6 x10^(-2) N.
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