大学物理-保守力与非保守力.ppt

1/12,一 万有引力和弹性力作功的特点 (The features of the work done by the universal gravitational & the elastic force),m对m的万有引力为,m移动dr时,F作元功为,1、万有引力作功 (Work done by universal gravitational force),2/12,m 从 A 到 B 的过程中F作功：,3/12,2、弹性力作功 (Work done by elastic force),弹性力,4/12,保守力所作的功仅决定于物体始、末位置,而与所经过的路径无关,二 保守力与非保守力 保守力作功的数学表达式(The conservative force & The non-conservative force The mathematical expression of work by the conservatiive force),The work done by the conservatiive force only depends on the initial & final positions of the object & is independent of the path that it took.,1 保守力作功的特点 (The feature of the work done by the conservative force),5/12,质点沿任意闭合路径运动一周时,保守力对它所作的功为零.,非保守力:力所作的功与路径有关(如摩擦力) .,When an object moves around an arbitrary closed loop the work done by conservative forces on it is zero,The non-conservative force:Work done by the force depends on the path(e.g The frictional force),2 保守力作功的数学表达式 (The mathematical expression of work by the conservative force),6/12,三 势能 (Potential energy),与相互作用的物体相对位置有关的能量.,Energy depends on of the relative position of the interactive objects,引力势能 Gravitional potential energy,引力的功 Work of gravitional force,弹力的功 Work of elastic force,弹力势能 Elastic potential energy,7/12,物体在地球表面附近距地面高为y时,具有的引力势能称为重力势能,保守力对物体作的功等于物体势能增量的负值,保守力的功(Work of conservative force),重力势能(Gravity potenial),The work done by the conservative force on object is equal to the negative value of the increment of the potenial energy of that object,8/12,在一维情况下,作用于物体上的在Ox轴上的保守力,等于势能对坐标x的导数的负值。,The conservative force acting on the object along the Ox axis is equal to the negative derivative of potenial energy with respect to the coordinate x,9/12,势能是状态的函数,讨论,The potenial energy is a function of state,势能具有相对性,势能大小与势能零点的选 取有关,任意两点间的势之能差却是绝对的.,The relativity of the potenial energy, the value of the potenial energy depends on the selection of the zero point,the difference of the potential energy between any two point has an absolute meaning,10/12,势能是属于物体系统的.,势能计算(Calculation of potenial energy ),The potenial energy belong to the system of objects,讨论,11/12,四 势能曲线(The potenial