Calculating Potential Energy of Three Point Charges

AI Thread Summary
The discussion focuses on calculating the potential energy of three point charges using the formula PE=k(q1q2/r + q1q3/r + q2q3/r), where k is 8.99e9. Participants emphasize the importance of using the correct distance "r" for each pair of charges and converting charge values to standard units (e.g., 2.9 microCoulombs to 2.9e-6 C). There is a mention of a mistake regarding the sign of the potential energy, which was initially calculated incorrectly. Clarifications are provided to ensure proper understanding of the calculations. The conversation highlights the need for attention to detail in physics problems involving multiple charges.
disque
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Homework Statement



Three point charges Q1 = 2.9 mu or micro C, Q2 = 4.9 mu or micro C and Q3 = 3.9 mu or micro C, are arranged as shown.

Homework Equations



PE=k(q1q2/r+q1q3/r+q2q3/r)
k=8.99e9

The Attempt at a Solution



By using that equation I plugged in the lengths and changed the 2.9 to micro coulombs.
 

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disque said:

Homework Equations



PE=k(q1q2/r+q1q3/r+q2q3/r)
k=8.99e9

The Attempt at a Solution



By using that equation I plugged in the lengths...
Sounds like you have the right idea. You realize that "r" is different for each pair of charges, right?

... and changed the 2.9 to micro coulombs.
I'm not sure what that means. Just use 2.9e-6 C, etc., for the charge values.
 
yea i got it, i had a negative sign and it was positive. not really sure why but thanks for your help
 

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