所谓“三法”即为分段法、填补法、重心移动法.利用分段法确定各部分物体的重力势能,则整体重力势能为各部分重力势能之和.填补法是将部分直接去掉,填补到原铁链底端,计算重力势能变化只需要计算填补移动部分的铁链重力势能的变化即可.重心法是求出始末状态的整个链条质心所在位置,直接由重力势能公式求解. The so-called “three methods” is the subsection method, the filling method, and the center of gravity movement method. Using the subsection method to determine the gravitational potential energy of each part of the object, the overall gravitational potential energy is the sum of the gravitational potential energy of each part. The filling method is to directly Remove, fill to the bottom of the original iron chain, calculate the change of the gravity potential energy only need to calculate the change of the gravity energy of the iron chain that fills the moving part. The center of gravity method is to find the position of the whole chain center of mass in the starting and ending state, and directly solve by the gravity potential energy formula. .