Physics Help Forum Coulomb's Law Help

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 Feb 4th 2017, 05:38 PM #1 Junior Member   Join Date: Feb 2017 Location: New York Posts: 2 Coulomb's Law Help Hello. I have been struggling over a homework assignment for a little while now. The question is as follows: Given the arrangement of charged particles in the figure below, find the net electrostatic force on the q1 = 5.25-µC charged particle. (Assume q2 = 12.33 µC and q3 = −14.12 µC. Express your answer in vector form.) The three charges (q1, q2, and q3) are located at the following points: q1: (-2.00cm, 0cm) q2: (1.00cm, 1.00cm) q3: (0cm, -1.00cm) I know that I need to compare q2 and q3 to q1 and then take some components of the vectors to get a final answer, but I dont seem to be getting the right answer and I'm almost out of submission attempts. Any help would be appreciated!
Feb 4th 2017, 09:08 PM   #2

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 Originally Posted by Daejoon Hello. I have been struggling over a homework assignment for a little while now. The question is as follows: Given the arrangement of charged particles in the figure below, find the net electrostatic force on the q1 = 5.25-µC charged particle. (Assume q2 = 12.33 µC and q3 = −14.12 µC. Express your answer in vector form.) The three charges (q1, q2, and q3) are located at the following points: q1: (-2.00cm, 0cm) q2: (1.00cm, 1.00cm) q3: (0cm, -1.00cm) I know that I need to compare q2 and q3 to q1 and then take some components of the vectors to get a final answer, but I dont seem to be getting the right answer and I'm almost out of submission attempts. Any help would be appreciated!
$\displaystyle F = \frac{k q_1 q_2}{r_{12}^2}$

First you will have to change the distances to m and the charges to C. The distance r12 must be in m and will be directed along the line from point 2 to point 1. So $\displaystyle r_{12} = \sqrt{(-0.02 - 0.01)^2 + (0 - 0.01)^2}$.

Now you need to have that force act along the line between the two charges. This will be given by $\displaystyle (-0.02 i - 0.01 j) - (0.01 i) = -0.03 i - 0.01 j$.

Putting this all together we get
$\displaystyle F_{12} = \frac{k q_1 q_2}{0.0316^2}$ in the direction -0.03 i - 0.01 j.

Give that a try and see what you can do. Let us know if you need more help than this.

-Dan
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Last edited by topsquark; Feb 4th 2017 at 09:18 PM.

 Feb 5th 2017, 10:34 PM #3 Junior Member   Join Date: Feb 2017 Location: New York Posts: 2 Got it right! Turns out, I kept messing up with adding the components... Anyways, thanks for clearing that up for me!

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