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

So now we're going to turn off the lights and I want to show you the motion of the center of mass.

我们要关上灯，我想给你们展示，质量重心的运动。

youdao

Use your hand to power the hoop in a back-and-forth motion: the hoop will alternate between hitting the center of your palm and the back of your hand.

用你的手来给呼啦圈前后移动的力：呼啦圈会在你的手掌心和手背上交替着力。

youdao

DeMille is considered the man who helped Hollywood become the center of the motion picture business.

VOA: special.2009.05.31

The steps get heavier and the speed increases until listeners are drawn into the movement of the rivers and the mills, the frenetic pace of an urban center in constant motion.

NPR: Time For Three: Beyond Classical

Of course, I remember Nortel having a big technology center up in Ottawa and Research In Motion (RIMM) spawning a bunch of new start-ups in Waterloo, Ontario.

FORBES: What's New in Canadian Tech? Increased Cross-Border Syndication Between Canadian and US VCs

Rajaratnam lost that motion before his trial but it is a center piece of his appeal.

FORBES: Will Rajaratnam Testify in Rajat Gupta Case?