An electron is accelerated inside a parallel plate capacitor. the electron leaves the negative plate with a negligible initial velocity and then after the acceleration it hits the positive plate with a final velocity β. the distance between the plates is 14.1 cm, and the voltage difference is 142 kv. determine the final velocity β of the electron using classical mechanics. (the rest mass of the electron is 9.11 x 10^-31 kg, the rest energy of the electron is 511 kev.) what is the final velocity β of the electron if you use relativistic mechanics?