In this study, Schulze collision inertial model was employed to investigate the effect of neglecting the negative inertial forces in collision efficiency and flotation rate constant predictions. The model evaluation was carried out with the Generalized Sutherland Equation (GSE) model in which the estimation of both positive and negative inertial forces have been well accounted. The general flotation kinetic model has been used in this study to demonstrate changes when the negative particle inertia is omitted. Theoretical comparisons were made on two minerals, i.e. quartz and chalcopyrite. The effect of particle density on the modified kinetic model was very significant when a dense mineral like galena was used. This reveals that the general flotation rate model is very sensitive to the substitution of Schulze model. Results obtained were far from satisfactory and show that the Schulze model cannot cope with the change of density very well. It was found that when Schulze collision model was implemented in flotation rate constant calculation, there is a wide range of particle size which is not strongly influenced by parameters such as bubble size and velocity, and particle density and results are very close to each other. This is not in good agreement with the experimental results or GSE model data. (C) 2017 Elsevier B.V. All rights reserved.