So I mentioned to you that the motion of the center of mass is very uniform in the absence of external forces, and that I can demonstrate for you again with the air track.

我向你们提到过,重心的运动是稳定的,若不受外力，我可以再次演示,在空气轨上。

youdao

A drop's existence can be understood in terms of its individual water molecules, the particular forces between them, and the general physical laws governing motion: quantum mechanics (QM).

在理解一滴水的存在时，可以依据它单个的水分子、分子之间的特定力量以及约束运动的一般物理法则，即量子力学。

youdao

It swirls, as circular motion in air masses is the response to conflicting forces, as seen in the circular motion of tornadoes and hurricanes.

就如我们所看见的龙卷风和飓风进行着圆形运动，由于气团应答着相互冲突的力量，大气层也在进行旋转运动。

youdao

But the reader comes away convinced that the forces set in motion, for good and for ill, in 1979 set the stage for the world we see today, in ways that were hard to see at the time.

WSJ: Book Review: Strange Rebels

In severing sex from procreation, humankind set into motion forces that have by now shaped and reshaped almost every aspect of life in the Western world.

WSJ: Has the Sexual Revolution Been Good for Women? Mary Eberstadt: No

And forces for monetary reform are very much in motion.

FORBES: Fiat Money: The Root Cause Of Our Financial Disaster