In this lecture, we will revisit the application of Newton's second law to a system of particles and derive some useful relationships expressing the conservation of angular momentum. Center of Mass Consider a system made up of n particles. A typical particle, i, has mass mi, and, at the instant considered, occupies the position Ti relative to a frame xyz. We can then define the center of mass, G, as the point

在解决线性方程组是否有解的判别条件之后, 我们知道在秩A=秩A=n(方程组未知量个数)时, 方程组有唯一解。在秩A=秩A