临界问题广泛地存在于中学物理中,每一个具体的临界问题都存在一个特殊的转换状态,这个特殊的转换状态称为临界态。临界态需满足一定的物理条件,这个物理条件称为临界条件。一般说来,不同的临界条件对应着不同的临界问题。然而很多的临界问题虽然物理过程或物理本质不同,却对应着同样的临界条件。根据临界条件的不同,将众多临界问题归类是分析解决临界问题的一种行之有效的方法。本文将就临界条件为“υ_(相对)=0”的一类临界问题归纳阐述。 一、υ_(相对)=0是运动物体上升还是下降的临界条件 大家知道,当运动物体在竖直向上方向做减速运动时,若其竖直向上的分速度为零,则物体到达最高点,这是以地为参照物得出的结论。当物体甲以另一运 The critical issue exists extensively in the middle school physics, and each specific critical issue has a special transition state. This special transition state is called the critical state. The critical state must satisfy certain physical conditions. This physical condition is called a critical condition. In general, different critical conditions correspond to different critical issues. However, many critical problems correspond to the same critical conditions, although the physical process or physical nature is different. According to the different critical conditions, categorizing many critical issues is an effective way to analyze and solve critical problems. This article summarizes a critical problem with the critical condition “υ_(relative) = 0”. One, υ _ (relative) = 0 is the critical condition of the moving object to rise or fall. We all know that when the moving object in the vertical direction to make a deceleration movement, if its vertical velocity is zero, the object reaches the highest point, This is a conclusion drawn from the ground as a reference. When an object is transported by another