Electric Field & Capacitor Problem...HELP!! An electron enters the lower left side of a parallel plate capacitor & exits at the upper right side making an upward curve. The initial speed of the electron is 4.00 x 10^6 m/s. The capacitor is 2.00 cm long, and its plates are separated by 0.150 cm. Assume that the electric field between the plates is uniform everywhere and find its magnitude. So I understand that F=ma=qE. I also understand that I can use kinematics to find the acceleration and I can also use the mass of an electron to figure out the force. However, how do I find q? I'm so confused!!! Please help! Thanks!!