柔软细绳的运动问题是大学物理力学课在“质点系的动量定理”的教学中常常涉及的典型类型之一，柔软细绳是日常实际绳索的简化的理想模型. 而理想模型的引入有时会出现在研究对象的某些点处的加速度变为无穷大，可称之为奇点. 若不考虑加速度奇点的影响常常产生错误. 本文借助柔软细绳运动的一个实例对此加以讨论.

Questions involving soft and thin cords’movement are a kind of model of college physics. A soft  and thin cord is an ideal model for the actual one，which makes the acceleration be infinite at some point of the soft and thin cord. This is the acceleration strange point. If the acceleration strange point is neglected，some mistakes may arise. A discussion is given here by an example of a soft and thin cord.