Abstract:Based on the momentum conservation law and the mechanical energy conservation law, the kinetic energy of an object sliding from an inclined plane was discussed under different inclination angles in both qualitative and quantitative ways,respectively. The practical application of the two theorems was studied in inertial and non-inertial systems contrastively. Through the analytical derivation and numerical analysis, the same results were obtained in two frames of reference, thus the range of application of the momentum conservation law and the mechanical energy conservation law was expanded, thereby.