In 1974 an unusual phenomenon called Usherenko effect was observed in impact experiments [1,2]. Surprisingly large were impact produced craters whose depth varied between 100 and 10000 times the impactor's size. For materials whose static strength is small or zero, e.g., sand or water, the depth of penetration is no larger than 100 times the size. When a macro-size body impacts on a barrier, it produces a crater whose depth is normally in a ratio of no larger than 6-10 to the body's size regardless impact parameters. The papers [1,3] give overviews of models which were developed to explain the phenomenon. They all try to answer why material resistance to the penetration of micro-size impactors suddenly decreases. We suggest a model that uses the concept of particle entrainment by a shock produced by the impact of a bunch of particles on a barrier. The approach was proposed by V.A. Simonenko . It is based on calculations by the finite-difference technique TWS [5,6]. Such an approach shows prospects for further development with account for new experimental results obtained after 1991. The goal of this paper is to demonstrate feasibility of applying this approach for justification of impactor's acceleration in solid.