  A second order relativistic hydrodynamic theory has been derived using
momentum dependent relaxation time in the relativistic transport equation. In
order to do that, an iterative technique of gradient expansion approach, namely
Chapman-Enskog (CE) expansion of the particle distribution function has been
employed. The key findings of this work are, (i) momentum dependent relaxation
time in collision term results in an extended Landau matching condition for the
thermodynamic variables, (ii) the result from numerical solution of Boltzmann
equation lies somewhere in between the two popular extreme limits : linear and
quadratic ansatz, indicating a fractional power of momentum dependence in
relaxation time to be appropriate, (ii) an equivalence has been established
between the iterative gradient expansion method like CE and the well known
moment approach like Grad's 14-moment method.
