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Homework Help: What is q and what is the charge (negative or positive)?

  1. Jan 19, 2016 #1
    HW one Physics 2.jpg
    Three identical point charges, each of mass m 0.10kg and charge q, hang from three

    strings, as pictured below. The lengths of the left and right strings are L 30.0cm

    and the angle is 45.0o.

    Just on looking at the picture I think the charge is positive since there is tension separation the three masses. I'm confused on how to get q. Should I be looking at the space separating the masses on the x-axis? or be more focused on gravity's role?
  2. jcsd
  3. Jan 19, 2016 #2


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    Draw a free body diagram for one of the side masses and consider the forces acting on it.
    It doesn't matter whether q is positive or negative. What matters is that the three charges are the same, including their signs.
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