This paper is aimed to present a set of numerical simulations of a penetrating collision, in which a small gas
core (the bullet) gets into a larger core (the target). The gravitational collapse, in the target core, is supposed to be ongoing
before the collision. After the collision, the integral properties of the resulting mixed gas core are calculated by using all
the SPH particles. Only three collision models are considered here according with their impact velocity, ranging from zero
to Mach 15. The outcomes of these collision models are presented only for two values of the impact parameter b. Such
collisions models allow to reveal how the occurrence of hydrodynamical instabilities favor the fragmentation of the cores
in their central region, pointing out the possibility to have a lot of small cloudlets. We show hereby that penetrating
collisions may have a major and favorable influence in the star formation process.