在复杂的物理过程中,某一物理量可能一直都在变化着.这种情况下,把整个过程分割为许多小过程或把研究对象分割成大量的微小单元,只要分割后的过程或单元足够小,对微小过程或单元就可以把变化的量看作恒量来处理,从而使问题得到解决,这就是 In a complex physical process, a certain physical quantity may always change.In this case, the whole process is divided into many small processes or the research object is divided into a large number of tiny units, as long as the partitioned process or unit is small enough , The tiny process or unit can be the amount of change as a constant to deal with, so that the problem is solved, this is