  We use Fermi liquid theory to study the mechanical impedance of 3He-4He
mixtures at low temperatures. The theory is applied to the case of vibrating
wires, immersed in the liquid. We present numerical results based on a direct
solution of Landau-Boltzmann equation for the 3He quasiparticle distribution
for the full scale of the quasiparticle mean-free-path. The two-fluid nature of
mixtures is taken into account in the theory, and the effect of Fermi liquid
interactions and boundary conditions are studied in detail. The results are in
fair quantitative agreement with experimental data. In particular, we can
reproduce the anomalous decrease in inertia, observed in vibrating wire
experiments reaching the ballistic limit. The essential effect of the
experimental container and second-sound resonances is demonstrated.
