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受约束的物体系统,在运动过程中的任一时刻,物体的速度大小之间一定存在着确定的数量关系,建立这种关系通常是分析问题的难点所在,本文将根据笔者的教学实践,根据物体间的约束关系进行速度分解,建立物体速度间的关系,而不是首先寻找分速度(或分运动)方向。 1 物体受到绳或杆的约束我们所研究的绳或杆一般都不考虑它们的形变,用绳或杆约束的两个(或两个以上)物体虽然在同一时刻速度一般不同,然而在不考虑绳和杆形变的条件下,物体沿绳或杆方向的分速度大小在同一时刻总是相等的,方向总是相同的,这就是绳与杆约束的基本特征,
In a constrained object system, there must be a certain quantitative relationship between the velocity of the object at any moment in the movement process. Establishing such a relationship is usually a difficult point for analyzing the problem. This article will be based on the author’s teaching practice. The constraint relationship between objects is speed-decomposed and the relationship between object speeds is established, instead of first finding the speed (or sub-movement) direction. 1 Objects are bound by ropes or rods. The ropes or rods we study generally do not take into account their deformation. Two (or more) objects constrained by ropes or rods, although at different speeds, are generally different, but they are not considered. In the condition of rope and rod deformation, the sub-velocity of the object along the rope or rod direction is always the same at the same moment, and the direction is always the same, which is the basic characteristics of the rope and rod constraints.