功、动能、动能的变化量及动能定理不但是高中物理的一个重要内容,也是学生学习的一个难点,特别是动能定理的使用条件不清楚.因此,本文将通过两个具体的物理过程来论述功和动能变化量的相对性与绝对性,并由此理解动能定理和能量守恒定律的适用范围. The change of kinetic energy, kinetic energy and kinetic energy are not only an important part of high school physics, but also a difficult point for students to learn, especially the conditions of use of kinetic energy theorems are not clear.Therefore, this article will discuss two specific physical processes Power and kinetic energy of the relative change and absolute, and thus understand the kinetic energy law and the law of conservation of the scope of application.