学生：既然用速度可以描述物体运动的快慢．为什么还要引入平均速度呢？教师：速度是用来描述物体运动快慢程度的物理量，速度大，表明物体运动得越快，即在相等的时间内通过的路程越长．在匀速直线运动中．速度的大小是始终不变的，因此可用速度值来描述物体的运动快慢；在变 Student: Since the speed can be used to describe the speed of the object movement. Why should we introduce average speed? Teacher: Speed ​​is a physical quantity used to describe how fast or slow an object moves. It has a large speed, indicating that the object moves faster, that is, the longer the distance traveled in an equal time. In uniform linear motion. The speed is always the same, so the speed can be used to describe the speed of the object;