that's a particle falling down under the affect of gravity.

这就是一个受重力作用下落的质点
If all you know

如果你只知道
is the particle is falling under the affect of gravity,

质点受重力作用下落
that's not enough to say where the particle is, right?

那并不足以表明物体的位移对吧
Suppose we all go to a tall building

假设我们都爬上一栋高楼
and start throwing things at various times and various speeds.

在不同时刻以不同速度抛出物体
We're all throwing objects whose acceleration is -g.

所有抛出物体的加速度都是 -g
But the objects are at different locations at a given time.

但是它们在同一时刻分别在不同的位置
That's because they could have been released from different heights

那是因为它们可能是从不同的高度
with different initial velocities.

以不同的初速度被抛出的
Therefore, it's not simply enough to say what the acceleration is.

因此仅知道加速度是多少是不够的
You have to give these two numbers.

你需要给出这两个量