Body mass index,or BMI, is a measure of a person's weight in relation to height.
VOA: special.2011.02.15
Well that process of control to maintain a constant environment inside our body, whether it's an environment of constant mass or constant composition, or constant temperature, is called homeostasis.
这个控制过程维持着,体内环境的恒定,不论是内环境中物质的量的稳定,或者成分的稳定,或温度的稳定,这种状态叫做内稳态
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
The World Health Organization defines obesity as a body mass index of thirty or more.
VOA: special.2011.02.15
First one says, if you knew the force acting on any body, without going into what caused the force, then you may set that force equal the mass times acceleration of the body.
第一部分是,如果你知道作用在任一物体上的力,无论这个力的来源是什么,都可以令力等于质量乘以物体的加速度
Here's the body of mass 3.
这就是那个 3 千克的物体
We can be precise about how much bigger by saying, "If the acceleration of a body to a given force is ten times that of a one kilogram mass, then this mass is one-tenth of one kilogram."
我们能精确地知道质量能大多少,只需要说,"如果物体在给定力作用下的加速度,是一个 1 千克物体的加速度的 10 倍,那这个物体的质量就是 1 千克的十分之一"
In fact, there's a property of gravitational fields anywhere, even in outer space, but there is some residual field between all the planets and all the stars in the universe, that the force on a body is proportional to the mass of the body.
实际上,这是任何地方的引力场都具备的属性,甚至是在外太空,在所有的行星和恒星之间,存在着某种剩余场,在这个场里作用在物体上的力,和物体的质量之间存在比例关系
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