Electric potential due to collection of charged particles

[Rijad Hadzic]

Homework Statement

A particle with charge q1 = -6.75x10^-6 is located at (0,3.25x10^-2 m ) and a second particle with charge 3.2x10^-6 is located at (0,-2.75x10^-2 m) what is the electric potential due to the two charges at the origin?

Homework Equations

V = kq/r

The Attempt at a Solution

So at the origin the potential should be kq1/r1 + kq2/r2 = k(q1/r1 + q2/r2)

plugging in, (8.99x10^9)(-1733785 + 1046109) = -6.87x10^5

but my book is telling me the answer is -8.21x10^5

what am I not taking into account here?

 

[TSny]

So at the origin the potential should be kq1/r1 + kq2/r2 = k(q1/r1 + q2/r2)

Good.

plugging in, (8.99x10^9)(-1733785 + 1046109)

I don't get the values shown in red.

 

[Rijad Hadzic]

Good.

I don't get the values shown in red.

Strange. I did the calculation a million times exactly like I just did it but I got the answer now... the mechanical task of calculating stuff makes me want to pull out my hair. I hope I don't do this on a test lol.

Anyways thank you..

 

[TSny]

OK, good. For the first charge, it looks like you used a distance of .035 m rather than .0325 m.