Physics 212
posted by Paula .
Three equal point charges, each with charge 1.50\mu C , are placed at the vertices of an equilateral triangle whose sides are of length 0.300m . What is the electric potential energy U of the system? (Take as zero the potential energy of the three charges when they are infinitely far apart.)
Use epsilon_0 = 8.85×10−12\frac{C^2}{N \cdot m^2} for the permittivity of free space.
how do I go about solving this problem? thank you very much for any guidance

potential energy is a scalar.
Take the first charge, move it. No energy change to move it.
Then move in the second charge, energy = kqq/d.
Now move the third charge in. It is opposed by the two other charge, energy= kqq/r * 2
add the energies: 3kqq/r
check my thinking.