1. The problem statement, all variables and given/known data My questions reads: An electron is pulled away from a fixed charge of 1.3μC. The electron is moved from the positive charge to 4.0 cm away from the charge. If the electron is released from the 4.0 c mark, what is the max velocity of the electron? 2. Relevant equations Ep = k q1q2/r - electric potential energy k = 9x10^9 q1 = -1.6 x 10^-19 C q2 = 1.3 x 10^-6 C r = 4.0 cm = 0.04 m Ek = 1/2 mv² - kinetic energy m = 9.11 x 10^-31 kg v = ? 3. The attempt at a solution Ep = Ek because all the electric potential energy is converted to kinetic energy when velocity is at its maximum. kq1q2/r = 1/2 mv² Since q1 is the charge of the electron, it is negative, so the left hand side of the equation is negative. That makes taking the square root impossible. But if I ignore the negative, I get the right answer in the text. Does that mean the sign of the Ep is not important, or that the magnitude (the absolute value) is all that matters? Or is it because the first equation should be the net energy =0 and the Ep gets moved algebraically and the negative disappears? The answer I get when I ignore the negative, and the answer given in the text is 3.2 x 10^8 m/s This is faster than the speed of light, which also confuses me a bit. Maybe just not a well written question?