所谓“二体问题”是指两个物体组成的系统,它们彼此仅以内力相互作用,而不受外力作用.因两物体都发生加速运动,所以在一般惯性系中方程比较复杂.若以其中一个物体为参照系在非惯性系中研究比较简单,但必须引入惯性力,引入惯性力后就可把二体问题化为单体问题来处理.现考查质量为m_1和m_2的两物体,它们不受外力,相互之间的作用力f_(12)和f_(21)遵守牛顿第三定律. The so-called “two-body problem” refers to a system composed of two objects that interact with each other only by internal forces and are not affected by external forces. Since both objects undergo acceleration, the equations in the general inertial system are more complicated. It is relatively simple to study an object as a frame of reference in a non-inertial frame, but inertial forces must be introduced. After the inertial force is introduced, the two-body problem can be treated as a single problem. Now examine two objects of mass m_1 and m_2. Without external forces, the forces f_(12) and f_(21) are in compliance with Newton’s third law.