  In this paper, we study the dynamics of a hollow spherical matter collapsing
with very large initial velocity. The spacetime is initially very similar to
the Vaidya solution, and the deviations from this background are treated
perturbatively. The equations of state for radial pressure $p_{\rm R}=k\rho$
and tangential one $p_{\rm T}=w\rho$ with constant $k$ and $w$ are assumed. We
find for the case of equations of state $k< 1$ and $0<w\leq1$ that the initial
velocity, which is nearly the speed of light, is strongly decelerated. This
result implies that the pressure is essential to the property of singularity
formation in gravitational collapse even for initially nearly light-speed
collapse. By contrast, in cases with the negative tangential pressure, the
present result implies that the central naked singularity similar to that of
the Vaidya spacetime can be formed, even though the radial pressure is
positive, and the weak, strong and dominant energy conditions hold. Especially,
in the case of $w<-(1-k)/4$, the high-speed collapse will produce the spacetime
structure very similar to that of the Vaidya spacetime.
