功是物理学中重要概念,它反映了力作用随空间积累的效应,学习这一概念除理解基本内涵外,具体应用时还要明确凡功必先判明是哪个力对哪个物体在哪一过程做的功(简称“三哪”),通常功问题的设置具有“递进式”特征,即某个力是否做功;做正功还是负功;做多少功,在此基础上还必须掌握以下注意点.一、做正、负功和不做功如何判断一般来说,如某个力与速度方向之间夹角为锐角则该力做正功,如夹角为钝角则做负功,如在某一过程中始终垂直,则做功为零,例如卫星绕地球做椭圆轨道运动,在向远地点运动过 Work is an important concept in physics. It reflects the effect of force accumulation with space. In addition to understanding the basic connotation of learning this concept, the specific application must also make clear where the force must first determine which force acts on which object The work done (referred to as “three where ”), usually work problem set has “progressive ” characteristics, that is, whether a force is doing work; doing positive or negative work; how much work to do, on this basis Must also master the following points. First, do positive and negative work and how to judge how to judge In general, such as a force and the angle between the direction of the acute angle is the power to do positive work, such as the angle is obtuse is done Negative work, such as in a certain process is always vertical, the work is zero, such as the satellite elliptical orbit around the Earth, moving to apogee