描述物体运动时要先选取参考系,理论上参考系的选择具有任意性,有时为了使运动的描述尽量简洁明晰、运算简单,我们可以巧妙地转换坐标系,从而使问题的解决得以简化。下面举例说明。例1一列行军队伍长120 m,通讯员从队尾赶到排头再返回队尾,这时队伍前进了288 m,如果队伍和通讯员都是做匀速直线运动,求通讯员在这段时间内共走了多远?方法一:常规解法设队伍运动速度为v,通讯员速度为nv,把整个过程分为追及和相遇阶段。追及过程通讯员从队尾赶到队首,将队伍长度简化为线段AB。绘制草图可知,通讯员的位移x_1减去队伍的位移x_2等于队伍长度l。故追及过程有 In order to describe the motion of an object, we should select the reference frame first. In theory, the reference frame is optional. Sometimes, in order to make the description of the motion as concise and clear as possible and simple to operate, we can skillfully convert the coordinate system to make the solution of the problem simple. Here’s an example. Example 1 A row of marching troops 120 m, the correspondent rushed to the front of the queue from the tail and then back to the tail, then the team advanced 288 m, if the team and correspondent are doing uniform linear motion, and seek correspondent altogether during this time How far? Method One: The conventional solution Set the team movement speed v, correspondent speed nv, the whole process is divided into chase and meet phase. Chase and process correspondent rushed to the front of the team from the beginning of the team, the length of the team simplified to AB. Sketched draw shows correspondent displacement x_1 minus team displacement x_2 is equal to the length of the team l. It is chasing the process