(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Nine different charged balls, which we treat as point charges, are arranged in a highly symmetric pattern around a square. Note that the value of Q is 4.00 x 10-6C, and L = 30.0 cm

Image: http://www.webassign.net/userimages/81224?db=v4net

2. Relevant equations

1) What is the magnitude of the net force experienced by the ball with the -3Q charge due to the +3Q and +Q charged balls only?

2) What is the magnitude of the net force experienced by the ball with the -3Q charge due to the four charged balls with charges of -5Q?

3 )What is the magnitude of the net force experienced by the ball with the -3Q charge due to the two charged balls with charges of +2Q?

4) Use your previous three results to find the magnitude of the net force experienced by the ball with the -3Q charge due to the other 8 charged balls.

3. The attempt at a solution

1)I got this part correct: I understand how to solve for the force when the point charges are in the straight line

My work is as follows:

F3 = F31 + F32

= k(-3Q)(Q) / L^2 + k(3Q)(+3Q) / 4L^2

= 5.25k(Q)^2 / L^2

= 8.39

2) and 3):

Here is where I do not understand how to solve for the force when there are diagonals involved.

If I am correct in my thinking for 2) then does the -3Q ball experience 2 diagonal forces from the 2 left -5Q balls and a straight force to the right from the 2 right -5Q balls?

In my calculation I did F53 = 15kq^2 / 3L^2, simplifying to 5kq^2 / L^2 which gives me 7.99 I believe. Since there are essentially 2 diagonal forces, do I multiply this by 2 and then add the other force which is directed right by doing 7.99cos(30 degrees)?

Thanks for all the input!

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# Homework Help: Calculating the magnitude of the net force bewteen charges

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