  Usually, hydrodynamic equations are restricted by the continuity and Euler
equations. However, the account of the higher moments of the distribution
function gives better description of the kinetic properties. Therefore, the
pressure tensor evolution equation (PTEE) is derived for spin polarized
degenerate fermions. Moreover, it is found that the pressure tensor enters the
interaction term generalizing the p-wave interaction in the Euler equation.
Hence, the PTEE allows to give a more accurate description of the interaction
in Euler equation. Next, the interaction is calculated for the PTEE. The
developed model is applied to the small amplitude bulk collective excitations
in homogeneous and trapped fermions in order to suggest the methods of
experimental measurement of the interaction constant of polarized fermions. It
is demonstrated that the anisotropy in the momentum space revealing in the
difference of the pressures in the anisotropy direction and the perpendicular
directions leads to a method of detection of the interaction constant.
