Abstract: In the methods for solving the equations of hydrodynamics, it is assumed that the mass forces are external and do not
depend on the fluid velocity. Here we consider the case when the mass forces depend on the velocity. Such forces are
friction forces, inertial forces, centrifugal forces, and Coriolis forces. It is used the statement proved by the author that
the centrifugal forces and the Coriolis forces are real forces. On this basis, mathematical models of such natural
phenomena as sea currents, tsunamis, dust whirlwinds, waterfalls, funnels, and whirlpools are proposed.