Moderation note: In reference to http://farside.ph.utexas.edu/teaching/336k/lectures.pdf Lagrangian(L) and Hamiltonian(H), Dear Greg I am studying the L and H. If kinetic energy(K) and potential(U) are given it seems that L=K-U. Hamilton defines (p_i, dot q_i being components of momentum, resp. velocity in i'th direction): H=sum p_i*dot q_i - L and it appears that for a conservative situation the Hamiltonian becomes H=K+U. With conservative one means usually U is a function of coordinates only. Do you think that this system would work for a mass-velocity relation? So a momentum which a changeble mass as a function of velocity v=Sqrt(sum (dot q_i)^2)? greetings.