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Homework Help: Coulomb's Law/Electric field questions

  1. Jan 20, 2010 #1
    I am not sure how to approach any of these.

    1- A 4.7-µC point charge is located at x = 0.9 m, y = 3.1 m, and a -3.9-µC point charge is located at x = 2.1 m, y = -1.9 m.
    (a) Find the magnitude and direction of the electric field at x = -2.7 m, y = 0.9 m. magnitude:
    direction: °

    (b) Find the magnitude and direction of the force on a proton at x = -2.7 m, y = 0.9 m. magnitude:
    direction: °

    2- An electron is released from rest in a weak electric field given by = -3.00 10-10 N/C . After the electron has traveled a vertical distance of 1.9 µm, what is its speed? (Do not neglect the gravitational force on the electron.)


    3- A fixed point charge of +2q is connected by strings to point charges of +q and +4q. Find the tensions T1 and T2. (Use q, d and k as necessary.)
    T1 =
    T2 =
     
  2. jcsd
  3. Jan 20, 2010 #2

    tiny-tim

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    Hi krtica! :wink:

    Show us what you've tried, and where you're stuck, and then we'll know how to help!

    Start with 1(a). :smile:
     
  4. Jan 20, 2010 #3

    In regards to question 1, I plotted each point on a x-y coordinate system. The three points form a right triangle. The opposite and adjacent lengths I took for each separate electric field. To find the magnitude of both, I used the Pythagoreum Theorem.

    Concerning the other questions, I am not really even sure where to begin.
     
  5. Jan 20, 2010 #4

    tiny-tim

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    ok, well, if it didn't give the right result, show us your calculations, and then we'll know how to help! :smile:
     
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