速度

在日常使用和运动学中，物体的速度是其速率（位置变化的速率）的大小；它因此是一个标量量。[1] 物体在一段时间内的平均速度是物体行进的距离除以时间间隔的持续时间；[2] 瞬时速度是平均速度的极限，当时间间隔趋近于零时。

In everyday use and in kinematics, the speed of an object is the magnitude of its velocity (the rate of change of its position); it is thus a scalar quantity.[1] The average speed of an object in an interval of time is the distance travelled by the object divided by the duration of the interval;[2] the instantaneous speed is the limit of the average speed as the duration of the time interval approaches zero.