在一本参考书上遇到过这样一道题:如图1所示,质量为2m和m的可看作质点的小球A、B.用不计质量不可伸长的细线相连,跨在固定的光滑圆柱两侧,开始时,A球和B球与圆柱轴心同高,然后释放A球,则B球到达最高点时的速率是多少?该书给出的答案是:把A、B两小球和轻绳看作一个系统,根据系统 Such a problem has been encountered in a reference book: as shown in Figure 1, the masses A and B that can be regarded as mass points of 2m and m are connected by thin lines that are not mass-inextensible and spanned. On both sides of the smooth cylinder, at the beginning, the A and B balls are at the same height as the cylinder axis, and then the A ball is released. What is the rate at which B ball reaches the highest point? The answer given in this book is: Put A, B Two balls and light ropes are considered as a system, according to the system