Electric potential energy and point charges problem

AI Thread Summary
The problem involves two point charges 2.0 cm apart with an electric potential energy of -149.9 µJ and a total charge of 28 nC. The equation used to relate these values is U = (kqQ) / r, where k is the Coulomb's constant. The negative potential energy indicates that one charge is positive and the other is negative, suggesting an attractive interaction. The discussion highlights the need to solve simultaneous equations to determine the individual charges, emphasizing the relationship between their magnitudes. The key challenge is correctly applying the equations to find the specific values of the two charges.
abeltyukov
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Hi,

Homework Statement



Two point charges 2.0 cm apart have an electric potential energy -149.9 µJ. The total charge is 28 nC. What are the two charges?


Homework Equations



U = (kqQ) / r

The Attempt at a Solution



U = -149.9 x 10^-6 = [(9 x 10^9)(28 x 10^-9 - q)(q)] / (0.02). Is that correct? I seem to get the wrong answer.


Thanks!
 
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This appears to be a simulateous equation problem. You don't know what either charge is, but you do know that the sum of both charges is 28 nC. (If I understand the problem correctly).

Since the PE is negative, that means one charge is + and the other is -. Therefore, how much more is the + charge's magnitude greater than that of the negative?
 
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