So, for example, if you were trying to study the motion of some object, here is one example.

举个例子,如果你想研究某个物体的运动,这里有个例子

耶鲁公开课 - 基础物理课程节选

But if I see you through the glass, the object is going on some trajectory, which has got both up and down and horizontal motion.

但是如果我透过窗户看到你,这个物体沿着某个轨迹运动,既有上下,也有水平方向的运动

耶鲁公开课 - 基础物理课程节选

You see an object in motion, you find a and you give a a certain numerical value, 10 meters per second squared.

你看到一个物体在运动,你会发现它的 a,然后给 a 赋值,10 米每秒平方

耶鲁公开课 - 基础物理课程节选