  In this note, we investigate the homogeneous radial dynamics of (Dp,
NS5)-systems without and with one compactified transverse direction, in the
framework of DBI effective action. During the homogeneous evolution, the
electric field on the D-brane is always conserved and the radial motion could
be reduced to an one-dimension dynamical system with an effective potential.
When the Dp-brane energy is not high, the brane moves in a restricted region,
with the orbits depending on the conserved energy, angular momentum through the
form of the effective potential. When the Dp-brane energy is high enough, it
can escape to the infinity. It turns out that the conserved angular momentum
plays an interesting role in the dynamics. Moreover, we discuss the gauge
dynamics around the tachyon vacuum and find that the dynamics is very
reminiscent of the string fluid in the rolling tachyon case.
