Small clarification: applying Coulomb's Law

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    Coulomb's law Law
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The discussion clarifies the meaning of subscripts in Coulomb's Law equations, specifically in the context of forces between electric charges. The subscripts (13 and 23) indicate the specific interactions between charge pairs: force F1 is from charge 1 to charge 3, and force F2 is from charge 2 to charge 3. Despite initial confusion, it is confirmed that these subscripts are simply identifiers for the forces involved. The formula itself remains unchanged, focusing on the relationship between the charges and the distances. This clarification helps in understanding the application of Coulomb's Law in the given example.
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Homework Statement


Hi,

I'm studying electric charges and fields, and I have a quick question about this example in my book:
Untitled-1_zps8eb88ce6.jpg



Everything is straightforward except the subscripts (13 and 23) on r in the denominators of initial Coulomb equations for F1 and F2. In the next step they just plugged in the distances, so those numbers don't seem to do anything, and there are no subscripts in the original formula. So what are they?


Homework Equations



F = k [(q1q2)/r2]
 
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They just indicate that the force one is from charge 1 to charge 3. And the force 2 is from charge 2 to charge 3.
 
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Duh, I knew it had to be something obvious. Thank you!
 

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