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

1. Sep 12, 2013

### DODGEVIPER13

1. The problem statement, all variables and given/known data

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.

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• ###### Homework 2.pdf
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2. Sep 12, 2013

### DODGEVIPER13

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

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• ###### EPSON003.jpg
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3. Sep 12, 2013

### 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.

4. Sep 12, 2013

### DODGEVIPER13

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

5. Sep 12, 2013

### DODGEVIPER13

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:

• ###### EPSON004.jpg
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110
6. Sep 12, 2013

### Staff: Mentor

I don't follow your working, but answer looks okay to me.

7. Sep 13, 2013

### DODGEVIPER13

Thanks I have moved onto 2.3 and broke it off onto another post as you has said earlier. Thanks again