Health officials say trials have gone smoothly and Australia could be the first country anywhere to start a mass immunization program.
VOA: standard.2009.08.25
I know that if the second mass moved faster than the first one, then the picture is completely wrong.
因为我知道如果第二个物体比第一个运动更快,那么受力图就肯定不是这样了
First is the body mass index, you're going to see this a lot and you--some of you probably know about it already because it's out there in the popular literature.
首先是体重指数,我们会经常碰到这个概念,你们也许已经知道这个概念了,它经常在科普读物中出现
General Motors was the first auto company in the United States to mass produce a modern electric car.
VOA: standard.2010.07.30
We'll first pick the body, with mass 3.
我们先来分析这个 3 千克的物体
So, let's go ahead and define our variables here, they should be familiar to us. We have the mass, first of all, me m is equal to m e, so that's the electron mass.
让我们继续定义这些常数,我们对这些应该都很熟悉了,首先,我们有质量,m等于。
For example, how do I know that when I pull the spring the first time for the mass, it exerted the same force when I pulled the spring the second time for the elephant?
例如 怎样才能知道,第一次连着物体拉弹簧时,产生的力和,第二次连着大象拉弹簧时产生的力是相等的呢
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