论文部分内容阅读
在中学物理教材及参考书中,经常会提到这样一个问题:为什么火车司机起动重载列车时,常常要先开一下倒车,然后再前进?这个问题的实质是一个静摩擦转化为滑动摩擦的问题。通常的定性解释是这样的:因为火车缓缓进站停止时,连结车厢跟车厢的铁钩是拉紧的(如图1所示),因此,机车要拖动列车向右驶出车站时,必须在同一时刻克服全部列车跟铁轨之间的静摩擦,这样,起动时比较困难。如果先开一下倒车,开始时它只要推动第一节车厢,为此也只要克服第一节车厢跟铁轨间的静摩擦,当继续运动时,第一节车厢跟铁轨间的摩擦减小了,然后机车和第一节车厢同时推动第二节车厢,如此继续下去,当全部列车向后移动时,
In the middle school physics textbooks and reference books, we often mention the following question: Why does a train driver often have to re-drive and then move forward when starting a heavy-duty train? The essence of this problem is the problem of the conversion of static friction into sliding friction. . The usual qualitative explanation is this: as the train slowly stops, the hooks connecting the carriages to the carriages are tightened (as shown in Figure 1). Therefore, when the trains are dragged to the right to exit the station, The static friction between all trains and railroad tracks must be overcome at the same time, which makes it difficult to start. If you start the reversing first, at first it only needs to push the first car. For this purpose, as long as the static friction between the first car and the rails is overcome, the friction between the first car and the rails is reduced when the car continues to move, and then The locomotive and the first car propel the second car at the same time. This continues and when all the trains move backwards,