“瞬时问题”常常伴随着这样一些标志性词语:“瞬时”、“突然”、“猛地”、“刚刚”等.求瞬时加速度,关键是确定物体的受力情况及运动状态.此类问题一般有两种基本模型:1.刚性绳模型:是指不发生明显的形变就 “Instantaneous issues” are often accompanied by such landmark words: “instantaneous,” “sudden,” “suddenly”, “just”, etc. For instantaneous acceleration, the key is to determine the object’s Force situation and movement state. There are two basic models for such problems: 1. Rigid rope model: means that no obvious deformation occurs