  We investigate the problem of forces on moving vortex in a superfluid or
superconductor. The main purpose is to locate the source which leads to the
contradictory results in the literature.
  We establish the connection between this problem to the difficult but well
studied subject of resistivity formula in transport theory.
  The relaxation time approximation used in the force calculation via
force-force correlation function is shown to be invalid.
  The roles of Berry's phase and fluctuation-dissipation theorems are
discussed.
