带电体在复合场中运动的问题是中学物理教学的难点,难就难在其物理情境多变、过程复杂、处理问题方法多样化、综合运用知识能力要求高。在这部分内容的习题教学过程中,笔者遇到了一个极有价值的疑难问题。习题是这样的:如图1所示,一个带正电的小球沿光滑的水平绝缘桌面向右运动,速度的方向垂直于一个方向为垂直纸面向外 The problem that the electrified body moves in the compound field is the difficult point of the physics teaching in the middle school. It is difficult to change the physical situation, the process is complex, the methods to deal with the problem are diversified, and the comprehensive utilization of the knowledge is required. In this part of the content of the exercise teaching process, I encountered a very difficult problem. Exercise is this: as shown in Figure 1, a positively charged ball along the smooth horizontal insulated table to the right, the direction of speed perpendicular to a direction perpendicular to the paper outward