Electric Potential and Potential Energy Exercise 1 . (a) What is the energy required to assemble the charge configuration shown below? . (b) Where on the axis could a hypothetical fourth charge 2q be placed so that the electric potential is 0 at the origin? . (c) If the -q charge has a mass m and is suddenly released from rest, it will be pulled up the y-axis by the other two charges. What is its speed when it gets to y = d? Ignore the hypothetical fourth charge. d