Write . For a slowly evolving circular Coulomb orbit, force balance and the mechanical energy give
The supplied Larmor formula therefore yields
Set . Since ,
Thus the classical radiation collapse of a Coulomb orbit obeys
The decreasing mechanical energy means a more tightly bound orbit, not a smaller speed. The formal collapse time is . The nonrelativistic, small-loss-per-orbit approximation eventually fails; the result demonstrates the classical instability rather than describing an actual hydrogen atom.