在物体运动状态变化的过程中,与物体运动状态有关的物理量有的是递增的,有的是递减的,有的是时增时减的,物理量增减的转折点称为临界状态,有关临界问题在物理学中是常见的,解决该类问题的关键是把握临界问题出现的条件,结合相应的物理规律,运用数学知识求解,或是把某个物理量推向极端(即极大或极小或极限位置)并依此作出科学的推理分析。一、静摩擦力的范围引出的临界问题 Some physical quantities related to the state of motion of an object are increasing, some decreasing, others increasing or decreasing in time, and the turning point of increasing and decreasing physical quantities is called a critical state. The critical problems are common in physics , The key to solving this kind of problem is to grasp the conditions for the emergence of critical problems, combine the corresponding laws of physics, apply mathematical knowledge to solve them, or push a certain physical quantity to the extreme (ie, the maximum or the minimum or the extreme position) and so on Make a scientific reasoning analysis. First, the scope of static friction leads to the critical issue