1. The problem statement, all variables and given/known data Three charged particles are placed at the corners of an equilateral triangle of side 1.20 m (see figure). The charges are Q1 = +3.5 µC, Q2 = -7.2 µC, and Q3 = -5.1 µC. Calculate the magnitude and direction of the net force on each due to the other two. (Assume the +x axis points to the right, that is, from Q2 toward Q3.) 2. Relevant equations F=kq1q2 / r2 3. The attempt at a solution It's a triangle with Q1 on top, Q2 on the bottom left and Q3 on the bottom right. For Q3: I have Q3 going up and left towards Q1, and going right due to Q2. So I have F31x as a negative number, F31y as positive, and F32x as positive. But my friend told me it's wrong, because it should be Q1 and Q2 moving towards/away from Q3, and Q3 is stationary. I thought it was the opposite; the other two forces are stationary and only Q3 moves. So I tried it again with F31x as positive, F31y negative, and F32x as negative. It's still wrong. I'm not sure what I'm doing wrong, please help? Thank you in advance.