题目

空间某区域内存在着电场，电场线在竖直平面上的分布如图所示，一个质量为m、电量为q的小球在该电场中运动，小球经过A点时的速度大小为v1，方向水平向右，运动至B点时的速度大小为v2，运动方向与水平方向之间的夹角为α，A、B两点之间的高度差与水平距离均为H，则以下判断中正确的是        A．若v2>v1，则电场力一定做正功     B．A、B两点间的电势差     C．小球由A点运动至B点，电场力做的功 D．小球运动到B点时，所受重力的瞬时功7、My dear students．I didn’t  know what I should say 76．            to some of you who is still addicted to the Internet． 77．            As teacher。I’d like to remind you that you’re 78．            wasting your time，energy，or even your life． 79．            You can never find the losing time and youth again． 80．            As students，we should value the limited time to study 81．            hard．As you know，you’11 graduate the school in two 82．            months or so．After graduation，you won’t  possibly 83．            find out so good a condition to study in．So make full use of every 84．             minute to study hard so that you won’t  feel sadly in the future． 85．            ．