College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 46

(a) Find the potential difference D Ve required to stop an electron (called a "stopping potential") moving with an initial speed of 2.85 × 10 7 m/s. (b) Would a proton traveling at the same speed require a greater or lesser magnitude potential difference Explain. (c) Find a symbolic expression for the ratio of the proton stopping potential and the electron stopping potential, V p / V e. The answer should be in terms of the proton mass mp and electron mass me.