  We study the medium-induced energy loss $-\Delta E_0(L_p)$ suffered by a
heavy quark produced at initial time in a quark-gluon plasma, and escaping the
plasma after travelling the distance $L_p$. The heavy quark is treated
classically, and within the same framework $-\Delta E_0(L_p)$ consistently
includes: the loss from standard collisional processes, initial bremsstrahlung
due to the sudden acceleration of the quark, and transition radiation. The
radiative loss {\it induced by rescatterings} $-\Delta E_{rad}(L_p)$ is not
included in our study. For a ultrarelativistic heavy quark with momentum $p
\gsim 10 {\rm GeV}$, and for a finite plasma with $L_p \lsim 5 {\rm fm}$, the
loss $-\Delta E_0(L_p)$ is strongly suppressed compared to the stationary
collisional contribution $-\Delta E_{coll}(L_p) \propto L_p$. Our results
support that $-\Delta E_{rad}$ is the dominant contribution to the heavy quark
energy loss (at least for $L_p \lsim 5 {\rm fm}$), as indeed assumed in most of
jet-quenching analyses. However they might raise some question concerning the
RHIC data on large $p_{\perp}$ electron spectra.
