An extension of the transverse-momentum analysis of P. Danielewicz and G. Odyniec is proposed. This extension involves a consideration of baryonic p_T-distribution widths in and out of the reaction plane. Calculations within one- and two-fluid mean-field models show that such an analysis allows us to extract more information on the nuclear equation of state and stopping power than the conventional one does. Different criteria for selecting central collisions are also examined. Selections according to the baryonic multiplicity in the midrapidity region and the transversal-to-longitudinal energy ratio are found to be suitable for this purpose. (orig.)Submitted to Nucl. Phys. AAvailable from TIB Hannover: RO 801(93-61) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman