Understanding Coulomb's Law: Calculating Force on a Line of Charges

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Coulomb's Law is applied to calculate the force on a line of charges, specifically focusing on the interaction between three charges: q1, q2, and q3. The confusion arises regarding the distances used to calculate forces F31 and F32, particularly the distance from q1 to q3. It is clarified that the values provided are the coordinates of the charges along the x-axis, not the direct distances between them. The correct distance from q1 to q3 is indeed 0.06m, but the calculations consider the positions of the charges. Understanding these coordinates resolves the initial confusion regarding the force calculations.
mr_coffee
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Hello everyone, I've been having the hardest time getting the hang of coulobs law. I got a physics book, physics for complete morons. The question is simple enough:

Consider a line of charges, q1 = 8.0 micro C at the orginin, q2 = -12 micro C at 2.0 cm, and q3 = 10 micro C at 4.0cm. What is the force on q3 due to the ohter two charges?

So you find F31 and u find the F32 and then add up the two forces to find your answer. But to find F31 they used a distance of .04m which confuses me. If the charges are as follows:

(q1)---(q2)-------(q3)
.02m .04m

Why wouldn't the distance from q1 to q3 be .06m? :bugeye:

Thanks.
 
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Yeah it is 0.06m, maybe you are misunderstanding what they are trying to do. What did they use for F32?
 
I suspect that those are the positions of the charges (their coordinates along the axis), not the distances between them. Calling it the x-axis, the charges are at:
x1 = 0m
x2 = 0.02m
x3 = 0.04m

Make sense?

And welcome to PF, by the way!
 
ahhh, how simple. Thanks Doc you were right!
 

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