2014.07.27【英译中】位移和速度(478词)

碎了翅膀 (donna) 路人甲
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发表于:2014-08-03 20:39 [只看楼主] [划词开启]

Displacement and Velocity

位移和速度

MOTION

运动

Motion happens all around us. Every day, we see objects such as cars, people,and soccer balls move in different directions with different speeds.We are so familiar with the idea of motion that it requires a special effort to analyze motion as a physicist does.

运动就在我们周围。每天,我们都能看到以不同方向不同大小的速度运动的像汽车,人们,足球这样的物体

One-dimensional motion is the simplest form of motion

一维运动是最简单的运动形式

One way to simplify the concept of motion is to consider only the kinds of motion that take place in one direction. An example of this one-dimensional motion is the motion of a commuter train on a straight track, as in Figure 1.

一种简化运动的概念的方式,就是只考虑往一个方向去的这类运动。一维运动的一个例子就是在直轨道上运动的通勤列车的运动,如图一所示。

In this one-dimensional motion, the train can move either forward or backward along the tracks. It cannot move left and right or up and down. This chapter deals only with one-dimensional motion. In later chapters, you will learn how to describe more complicated motions such as the motion of thrown baseballs and other projectiles.

在这个一维运动中,火车可以沿着轨道向前或是向后运动。他不能向左或是向右向上或是向下运动。这一章仅仅处理一维运动问题。在以后的章节中,你可以学到如何描述更多的复杂运动,比如被扔出去棒球或是其它抛体的运动。

Motion takes place over time and depends upon the frame of reference

运动的发生需要经历时间,并且取决于参照系

It seems simple to describe the motion of the train. As the train in Figure 1 begins its route, it is at the first station. Later, it will be at another station farther down the tracks.

描述那列火车的运动好像很简单。图一的火车开始它的航程,首先他在第一站,然后,他在沿着轨道远处的另一站。

But Earth is spinning on its axis, so the train, stations, and the tracks are also moving around the axis. At the same time, Earth is moving around the sun. The sun and the rest of the solar system are moving through our galaxy. This galaxy is traveling through space as well.

但是地球是绕着地轴自转的,所以火车站台还有轨道都在绕着地轴运动。同时,地球在围着太阳转,太阳和整个太阳系都在银河系中运动。而银河系也在空间中运动。

When faced with a complex situation like this, physicists break it down into simpler parts. One key approach is to choose a against which you can measure changes in position.

在面对这样的复杂状况时,物理学家把它分解成更加简单的部分,最关键的方法是选取一个你可以计量位置变化的参照系。

In the case of the train, any of the stations along its route could serve as a convenient frame of reference. When you select a reference frame, note that it remains fixed for the problem in question and has an origin, or starting point, from which the motion is measured.

在火车这个例子中,任何沿着它航线的站台可以当作是一个方便的参照系。当你选择参照系的时候,注意它在整个问题中是保持固定的,而且他还要有一个原点,或者叫起始点,运动从这一点开始计算。

 If an object is at rest (not moving),  its position does not change with respect to a fixed frame of reference. For example, the benches on the platform of one subway station never move down the tracks to another station.

如果一个物体是静止的(不动的),它的位置不会在固定的参照系上发生变化。比如,一个火车站站台上的长椅就不会顺着轨道移动到了另一个站台。

 In physics, any frame of reference can be chosen as long as it is used consistently. If you are consistent, you will get the same results, no matter which frame of reference you choose.

在物理学中,只要能够固定地使用,怎么选择参照系都可以。只要你选了之后就固定了,你总能得到相同的结果,不管你选择的参照系到底是哪个。

 But some frames of reference can make explaining things easier than other frames of reference. For example, when considering the motion of the gecko in Figure 2, it is useful to imagine a stick marked in centimeters placed under the gecko’s feet to define the frame of reference. The measuring stick serves as an x-axis. You can use it to identify the gecko’s initial position and its final position.

但是有些参照系的选择就比其它一些参照系在解释问题时更容易。比如,当考虑图2中的壁虎的运动时,想象出来一个在壁虎的脚下有一个刻着厘米刻度的棍子,把这个棍子当作参照物会更有用。这个测量的棍子就是一个X轴。你能用这个来定义壁虎的初始位置和末态位置。

 

分类: 英语
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