Physics Problem?

Question

An electron and a proton are initially very far apart (effectively an infinite distance apart). They are then brought together to form a hydrogen atom, in which the electron orbits the proton at an average distance of 5.32 10-11m. What is EPEfinal - EPEinitial, which is the change in the electric potential energy?
J

Answer 1

The initial EPE is 0 since the particles are infinately apart. When they come together, the EPE (i'll use U) is given by:

U = kq1q2/(r^2) = -ke^2/r^2 = -k(e/r)^2

k = 9*10^9
e is the unit charge and r is the atomic radius