[en] The tidal force effects of a spherical galaxy passing head-on through a disk galaxy have been studied at various regions of the disk galaxy and for various orientations of the disk galaxy with respect to the direction of relative motion of the two galaxies. The density distribution of the disk galaxy is taken to be, sigma(r) = sigma-c e^-4sup(r)sup(/)sup(R), where sigmasub(c) is the central density and R is the radius of the disk. The density distribution of the spherical galaxy is taken to be that of a polytrope of index n = 4. It is found that as a result of the collision, through the central parts and the outer parts of the disk galaxy remain intact, the region in between these two regions disrupts. Thus a ring galaxy with a nucleus embedded in the ring -i.e., a ring galaxy of the RN-type, is formed. (orig.)