Hi, this is my first time posting here but I have a question that looked really simple at first, but the answer I get is wrong from the answer given to us by our teacher.(adsbygoogle = window.adsbygoogle || []).push({});

The question is this:

Consider the diagram below

http://img485.imageshack.us/img485/9282/physics3bn.jpg [Broken]

a) What is the electric potential energy of the system?

What I did

3x10^-6=q1

1x10^-6=q2

-2x10^-6=q3

Epotental(total)= (Epotential @ q1) + (Epotential @ q2) + (Epotential @ q3)

=[(kq1q2)/0.36 + (kq1q3/0.36)] + [(kq2q1/0.36) + (kq2q3/0.4)] + [(kq3q1/0.36) + (kq3q2/0.4)]

I used the formulaE=(kq1q2)/rto get the potential energies at all 3 points and then added them together. I got -0.24 J but the answer the teacher gave us is -0.12J. Is it possible he is mistaken, or am I oversimplifying this question?

BTW: This is grade 12 physics

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# Homework Help: Electric Potential Energy Question

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