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在不少的参考资料上有类似这样一道题目:一块焦距为f=20厘米的凸透镜直立在一辆小车上,两者的总质量为0.5千克,小车放置在光滑的水平面上,如图1所示.透镜正前方30厘米处,直立着线状物体AB,若用水平力F=0.125牛作用在小车上,试求在加上F之后的2秒内,AB所成的象移动的平均速度. 题目给出的答案是8.33厘米/秒,显然是指物体AB的象沿主光轴方向的平均速度.然而,有的学生问到,物体AB上各个发光点经透镜
There is a similar topic on many reference materials: a convex lens with a focal length of f=20 cm is erected on a small vehicle with a total mass of 0.5 kg. The trolley is placed on a smooth horizontal surface, as shown in Figure 1. Indicating that the linear object AB is erected 30 cm in front of the lens, and if the horizontal force F=0.125 N is applied to the dolly, the average moving speed of the image formed by the AB within 2 seconds after adding F is determined. The answer given in the title is 8.33 centimeters per second. Obviously it refers to the average speed of the image of the object AB along the main optical axis. However, some students have asked that each luminous point of the object AB passes through the lens.