College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 16

The nonrelativistic expression for the momentum of a particle, p = mv , can be used if v c. For what speed does the use of this formula give an error in the momentum of (a) 1.00% and (b) 10.0%
(a) Show that a potential difference of 1.02 × 10 6 V would be sufficient to give an electron a speed equal to twice the speed of light if Newtonian mechanics remained valid at high speeds. (b) What speed would an electron actually acquire in falling through a potential difference equal to 1.02 × 10 6 V