More Discussion about the Loading and Loaded Body of Inertia Force

Inertia force occurs under two different circumstances: one is when the equation of dynamics for a particle is to be built under a noninertia reference frame, the other occurs when using the method of dynamic equilibrium (d′Alembert′s principle) to solve a dynamical question. Compare these two kinds of inertia force carefully and then it will be found that they are different conceptions, between which there are obvious differences. The inertia force which occurs when equations of dynamics are to be built has loading body but no loaded body. But in the d′Alembert′s principle,all inertia forces are interactions between two objects, so they have loading body and loaded body. [WT5HZ]