我们在利用物理知识解决实际问题时,往往会牵扯到描述某一过程或者某一状态的物理量在其发展中的变化.然而,这些问题又往往会由于受到物理规律和条件的制约,其取值往往只能在一定的范围内变化,求这些量的值的问题便可能涉及到要求求解物理量的极值.1问题引出如图1所示,M、N为两个完全相同的质量分布均匀的小球,AB为MN连线的中垂线,有一个质量为m的小球从MN连线的中点O沿OA方向运动,则它 When we use physics knowledge to solve practical problems, we often involve the changes that describe the physical quantities of a process or a certain state in its development. However, these problems are often constrained by the laws and conditions of physics. Often only within a certain range of changes, the value of these quantities may involve the need to solve the physical value of the extreme.1 The problem leads to Figure 1, M, N are two identical uniform mass distribution Ball, AB is the vertical line of the MN connection, there is a ball of mass m moving in the OA direction from the midpoint O of the MN connection, then it