i didnt read any text on this but few months ago, i just thought it might b as follows---
*what you do for body moving with non realistivitic speed--------
KINETIC ENERGY = integration of mv.dv = 1/2 mv2
but any body moving with a speed of light can move faster than light so there is no possibility of integrating v.dv
so v.dv in this case will become v.v which is nothing but mv2 or mc2
i didnt read any text on this but few months ago, i just thought it might b as follows---
*what you do for body moving with non realistivitic speed--------
KINETIC ENERGY = integration of mv.dv = 1/2 mv2
but any body moving with a speed of light can move faster than light so there is no possibility of integrating v.dv
so v.dv in this case will become v.v which is nothing but mv2 or mc2