Question

what is the amount of workdone by a electron moving half of the speed of the light in empty space free of all forces

Answer 1

since all force is zero so work done by electron is will be zero .
as we know that
W =F.S
F=0 then
W=0

Answer 2

since all force is zero so the work done by electron will be zero

as we known that

W =F*S

F =0

then

W= 0