[dleviwing]

Duane;
As an object is accelerated, its mass value increases. This is referred to as Relativistic mass (Einstein's equation). This should not be confused with the assumed "Rest Mass" inferred by the equations for particles.

For a better understanding of the development of the equations and concepts you've alluded to, I can suggest an excellent text:
"Sourcebook On Atomic Energy" by Samuel Glasstone.