We present an analysis of the location of interacting E/S0 galaxies on theFundamental Plane (FP). Using the NEMO package, we performed N-body simulationsof close encounters and mergers of two self-gravitating spherical galaxies. Twomodels for encounting galaxies - Plummer's and Hernquist's - were used. Thenumber of particles ranged from 20000 to 50000 per galaxy. The changes ofcentral density, half-mass radius and central velocity dispersion wereanalysed. It was found that close encounters between galaxies alter noticeablythe above parameters within a very short time interval (10^7 - 10^8 years) justbefore the final merger. The amplitudes of parameter changes strongly depend onthe initial mass concentration of a model. In some experiments we considered anencounter of two spherical galaxies with dark matter components. The effect ofparameter changes was less pronounced than for the experiments without a darkhalo. The results of the simulations were used to discuss the FP forinteracting early-type galaxies.
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