I am still trying to derive all the relations in relativistic mechanics, and have narrowed one of my problems down to the following. If E = m (c=1), then shouldn't dE/dt = dm/dt ? The left side of that equation is the work done on the particle per unit time, or the velocity vector -dot- force vector. I have been unable to get the right side of that equation to also equal that simple expression for power. I get (m*(u -dot- du/dt)) / (1-u^2) instead of the time derivative of the momentum vector (dp/dt), etc. Any ideas on how to show that? Thanks. PS. m=m_o/sqrt(1-u^2), p=mu, vectors, etc.