Space mag lev.

There is a 1 kilogram mag lev train in space that propels itself by converting 1 joule of electric energy into kinetic energy per second. There is no resistance and the train's mass remains constant during the experiment. What is it's acceleration?

as E->infinity, a->0 from a frame that was at rest in relation to the object at t=0,  the reason for this is that as the object approaches relativistic speeds, the energy starts going into a mass increase rather than a speed increase, as the object can never reach the speed of light.