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曲线运动的线速度方向是其轨迹上任一点的切线方向.这个情况教材上是用刀具磨砂轮来演示.但农村中学常常难以找到砂轮,故建议作如下的改进:如图1所示,剪一片圆形硬纸片直径约5厘米,中间插入一段短的铅笔,做成一个陀螺,在桌面上放上一张白纸,让陀螺在纸上旋转,然后用钢笔(或吸管)在旋转的纸片上滴墨水,就可以看到墨水飞出时落在纸上的痕迹都跟圆周相切.该实验取材容易,操作简单,现象明显.
The linear velocity direction of the curve motion is the tangential direction of any point on its trajectory. In this case, the teaching tool is used to demonstrate the tool grinding wheel. However, it is often difficult for rural middle schools to find the grinding wheel. Therefore, the following improvements are proposed: A circular cardboard piece is about 5 cm in diameter. A short pencil is inserted in the middle to make a gyro. Place a white paper on the tabletop and let the top rotate on the paper. Then use a pen (or straw) on the rotating paper. Dropping ink on the film, you can see that the traces of ink falling on paper when flying out are all tangent to the circumference. This experiment is easy to draw, simple to operate, and phenomenal.