Comment on 'Towards addressing transient learning challenges in undergraduate physics: An example from electrostatics'

Abstract

We make some crucial remarks about the recent presentation by Fredlund et al (2015 Eur. J. Phys. 36 055002) considering the tutorial problem raised therein. After working out the velocity of the electron (we also included the role of image charges or induced charges) as it strikes the (conducting) metal sphere, we found the velocity value is already near the relativistic regime. The latter then encounters the open issue; to obtain a classical equation of motion of a point charge for which Yaghjian (2008 Phys. Rev. E 78 046606) has mentioned the following difficulty: the electrostatic energy of formation and thus the electrostatic mass of a point charge is infinite.