"First of all, I want everybody here to be careful about what you post on Facebook because in the YouTube age, whatever you do, it will be pulled up again later somewhere in your life.

VOA: special.2009.09.14

You'll recall that at the very end of class we pulled up this little demo that looked like this.

你们可以回忆一下，我们曾,有个这样的演示。

哈佛公开课 - 计算机科学课程节选

Dynamics then tells you why the object goes up, why the object goes down and why is it pulled down and so on.

而动力学则会告诉你为什么物体向上运动,为什么向下运动,为什么停下来,等等

耶鲁公开课 - 基础物理课程节选