  This paper is concerned with a nonholonomic system with parametric excitation
- the Chaplygin sleigh with time-varying mass distribution. A detailed analysis
is made of the problem of the existence of regimes with unbounded growth of
energy (an analogue of Fermi's acceleration) in the case where excitation is
achieved by means of a rotor with variable angular momentum. The existence of
trajectories for which the translational velocity of the sleigh increases
indefinitely and has the asymptotics $\tau^{\frac{1}{3}}$ is proved. In
addition, it is shown that, when viscous friction with a nondegenerate Rayleigh
function is added, unbounded speed-up disappears and the trajectories of the
reduced system asymptotically tend to a limit cycle.
