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在一次测试中,笔者选用了下面这道题:如图1所示,长木板 AB 放在水平面上,它的下表面光滑,上表面粗糙.一个质量为 m、电荷量为 q的小物块 C 从 A 端以某一初速度向右滑上木板,当存在竖直向下的匀强电场时,C 恰能滑到 B 端,若将电场改为竖直向上,大小不变,C 只能滑到 AB 的中点.取重力加速度为 g,试求此匀强电场场强 E 的大小.
In one test, the author chose the following question: As shown in Figure 1, the long board AB is placed on a horizontal plane, its lower surface is smooth, and its upper surface is rough. A small mass C with mass m and charge q Slide the board from the A end to the right at a certain initial speed. When there is a vertically downward uniform electric field, C can just slide to the B end. If the electric field is changed to the vertical direction and the size is not changed, C can only Slide to the midpoint of AB. Take the gravitational acceleration as g, and try to find the intensity of the E field strength of this uniform electric field.