[en] The nucleon-nucleus interaction is considered within the framework of the resonating-group method (RGM), but with the simplifying assumptions of omitting target-recoil effects and core-exchange contributions. The resulting model, called model K, contains then only direct and knock-on-exchange terms. Comparisons between RGM and model-K results in n+α, n+¹⁶O, and n+⁴⁰Ca systems for bound-state energies, phase shifts, differential scattering cross sections, and polarizations show that model K works very well when the target nucleus has a nucleon number greater than about ten and when the scattering energy is higher than about 10 MeV. Because of the adoption of these simplifying assumptions, general expressions for the nuclear-central, Coulomb, and spin-orbit parts of the nucleon-nucleus nonlocal potential can be analytically derived without much difficulty. These expressions have simple forms and are suitable for a systematic and large-scale analysis of existing scattering data even in cases where heavy target nuclei are involved