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Find the electric field and force at a point in 3d space

  1. Sep 12, 2013 #1
    1. The problem statement, all variables and given/known data
    Uploaded Problem 2.1


    2. Relevant equations
    Etotal=Eq1+eq2


    3. The attempt at a solution
    On problem 2.1 I need quite a bit of help here. I am not really sure how to approach this I have done some work but it is highly incorrect. I hand wrote my solution, so I will upload that too.
     

    Attached Files:

  2. jcsd
  3. Sep 12, 2013 #2
    Here is my redo I saw a problem in the book that looked kinda close so i tried to follow it but it really wast that close in the end
     

    Attached Files:

  4. Sep 12, 2013 #3

    gneill

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    Staff: Mentor

    Your second attempt is better as it is taking the vectors into account, but I think you're trying to do too much at once.

    Start by reducing the Coulomb constant to a single constant: ##k = \frac{1}{4 \pi \epsilon_o}##. That way you don't need to drag the whole thing through the calculations.

    Next, Deal with one charge at a time. Find the field at the point in question due to Q2 alone, since it's a fixed feature. Call that E2.

    Then find the contribution by Q1, leaving just the Q1 as a variable (so you'll end up with some vector constant, say D, multiplied by Q1 to yield the vector components of the E-field due to Q1 at the point in question). Call that E1.

    At this point you should be able to deal component-wise with the various E vectors to address the requirements of the questions.
     
  5. Sep 12, 2013 #4
    well I figured it out but thanks for the reply I get Q1=-8.323 nC and Q1=-45nC. Well I didnt figure it out but I saw a solution I understood
     
  6. Sep 12, 2013 #5
    hey can you check my 2.2 answer though I feel that it is right I get 40nC. Sorry my upload wasnt super clear!
     

    Attached Files:

  7. Sep 12, 2013 #6

    gneill

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    Staff: Mentor

    I don't follow your working, but answer looks okay to me.
     
  8. Sep 13, 2013 #7
    Thanks I have moved onto 2.3 and broke it off onto another post as you has said earlier. Thanks again
     
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