  We have presented in this communication a new solving procedure for
Kelvin-Kirchhoff equations, considering the dynamics of the falling or
ascending the rigid disc in an ideal incompressible fluid, assuming
additionally the dynamical symmetry of rotation for the falling or ascending
body, I_1 = I_2. Fundamental law of angular momentum conservation has been used
for the aforementioned solving procedure. The system of Euler equations for
dynamics of disc rotation has been explored in regard to the existence of an
analytic way of presentation for the approximated solution (where we consider
the case of laminar flow at slow regime of deceleration of the symmetric disc
rotation). This scenario is associated with consideration of that the Stokes
boundary layer phenomenon on the boundaries of the body has also been assumed
at formulation of basic Kelvin-Kirchhoff equations. It allows us to use the
results of Jeffery fundamental work, in which analytical solution for rotations
of spheroid particle in Euler angles was obtained. The results of calculations
for the components of angular velocity should then be used for solving momentum
equation of Kelvin-Kirchhoff system.
