1 p(r,z)=-- q() (-2) +r It should be emphasized that the free surface is assumed to be located at z = 0, approximately at the same place where it was at the moment of the bullet impact, which is a good approximation for sufficiently slender bullets. L 47 ay ar bullet surface de. The strength of the sources distributed over the submerged and mirror-reflected axis of the bullet is established using the fact that the bullet surface is impenetrable for blood and thus 2 1 q() 27 bullet surface (3) (4)