  We study forced oscillations of a rod with a body attached to its free end so
that the motion of a system is described by two sets of equations, one of
integer and the other of the fractional order. To the constitutive equation we
associate a single function of complex variable that plays a key role in
finding the solution of the system and in determining its properties. This
function could be defined for a linear viscoelastic bodies of
integer/fractional derivative type.
