Hi I wanted to know for which cases the Euler Lagrange equations are applicable? 1.) Imagine that we have a kinetic Energie T(q,q') and a potential that also depends on velocity V(q,q'). As far as i know the Euler Lagrange equations for a particle still hold in this case, is that true? Now: 2.) Imagine that I have two particles with velocities v1 and v2 and imagine that the non holonomic constraint v1-v2=0 holds. and they are both placed in an external potential that depends on both, the velocities and positions of the particles. how would the euler lagrange equations look like?