《帕斯卡尔法》

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Did you ever watch someone make balloon animals like this turkey? When you blow up a balloon, you force air inside the balloon through a small opening. The air spreads out and presses against the inside of the balloon, forcing it to expand. Pressure always spreads throughout a contained fluid like air in a balloon.
::你有没有看过有人制造像这只火鸡这样的气球动物?当你吹气球时,你将气球中的空气通过一个小孔强制进入气球中。空气向气球内部扩散,并按压气球,迫使气球膨胀。压力总是在气球中像空气一样的封闭液体中扩散。

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Pressure and Force
::压力和力

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Pressure is the amount of force acting on a given area. It is represented by the equation:
::压力是指在给定区域上作用的强度。它由方程式表示:

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$\begin{array}{r}\mathrm{P}\mathrm{r}\mathrm{e}\mathrm{s}\mathrm{s}\mathrm{u}\mathrm{r}\mathrm{e}=\frac{\mathrm{F}\mathrm{o}\mathrm{r}\mathrm{c}\mathrm{e}}{\mathrm{A}\mathrm{r}\mathrm{e}\mathrm{a}}\end{array}$
::压力=力量

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The pressure exerted by a fluid increases if more force is applied or if the same force is applied over a smaller area. The equation for pressure can be rewritten as:
::如果施用更大的力力或对较小的区域施用同样的力,液体施加的压力会增加。

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Force = Pressure × Area
::力 = 压力x区域

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This equation shows that the same pressure applied to a greater area increases the force.
::这一方程式表明,对更大的面积施加同样的压力会增加力量。

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Pascal and His Law
::帕斯卡尔和他的法度,

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Some of the earliest scientific research on pressure in fluids was conducted by a French mathematician and physicist named Blaise Pascal (1623–1662). The SI unit of pressure, the Pascal (Pa), is named for him because of his important research. One of Pascal’s major contributions is known as Pascal’s law . This law states that a change in pressure at any point in an enclosed fluid is transmitted equally throughout the fluid.
::法国数学家和物理学家布莱斯·帕斯卡尔(Blaise Pascal)(1623-1662年)对液体压力进行了一些最早的科学研究。 SI压力单位帕斯卡尔(Pa)因其重要研究而命名为他。 帕斯卡尔(Pa)的主要贡献之一被称为帕斯卡尔(Pascal)的法律。 这部法律规定,封闭液体在任何一点的压力变化在液体中平等传递。

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A Simple Example
::简单示例

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A simple example may help you understand Pascal’s law. Toothpaste is a fluid that is enclosed in a tube with a small opening at one end. Look at the toothpaste tube in the Figure . When any part of the tube is squeezed, toothpaste squirts out the open end. The pressure applied to the tube is transmitted equally throughout the toothpaste. When the pressure reaches the open end, it forces toothpaste out through the opening.
::简单的例子可以帮助您理解帕斯卡尔的法律。 牙膏是一种液体,它被封闭在一端有一个小开口的管子中。 看看图中的牙膏管子。 当管子的任何部分被挤压时,牙膏会从开口端吐出。 牙膏施加在管子上的压力在牙膏上同样传遍整个牙膏。 当压力达到开口端时,它会迫使牙膏通过开口流出。

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Using Fluid Pressure
::使用流流压

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The ability of fluids to transmit pressure in this way can be very useful—besides getting toothpaste out of a tube! For example, hydraulic brakes in a car use fluid to transmit pressure, and when they do, they also increase force. You can see how hydraulic brakes work in the Figure .
::液体以这种方式输送压力的能力可能非常有用——除了从管子里取出牙膏之外!例如,汽车液压刹车使用液压来输送压力,当它们这样做时,它们也会增加力量。你可以看到液压刹车在图中是如何工作的。

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Q : In this diagram, how can you tell that the force applied by the brake cylinder is greater than the force applied by the brake pedal mechanism?
::问题:在本图中,你如何知道刹车制动器所施的力大于刹车制动装置所施的力?

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A : The arrows representing the force applied by the break cylinder are larger than the arrow representing the force applied by the brake pedal mechanism. A larger arrow indicates greater force.
::A: 代表破碎气瓶所施力的箭头大于代表刹车踏板装置所施力的箭头。更大的箭头表示更大的力。

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Q : How do hydraulic brakes increase the force that is applied to the brake shoes?
::问题:液压刹车如何增加用于制动刹车的力?

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A : The pressure exerted by the fluid on the brake shoes is applied over a larger area. When pressure acts over a larger area, it increases the force (Force = Pressure × Area).
::A:制动鞋上的液体所施加的压力在更大的区域施压。当压力在更大的区域施压时,就会增加力(力=压力x区域)。

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Hydraulic car lifts also use fluid to transmit pressure and increase force. The lifts are used to raise cars, which are very heavy, so mechanics can work on them from underneath. Controls in airplanes use fluids to transmit pressure and increase force so a flick of a switch can raise or lower heavy landing gear. 
::液压汽车电梯还使用液压来输送压力和增强力。 电梯用来提升非常重的汽车,因此机械师可以从下面对汽车进行操作。 飞机的控制用液来输送压力和增加力,这样开关的闪烁就可以提高或降低重型起落装置。

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Summary
::摘要

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• Pascal’s law states that a change in pressure at any point in an enclosed fluid is transmitted equally throughout the fluid.
  ::Pascal的法律规定,封闭液体在任何一点的压力变化,在整个液体中平等传递。
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• The ability of fluids to transmit pressure in this way can be very useful—from getting toothpaste out of a tube to applying the brakes on a car.
  ::液体以这种方式输送压力的能力可能非常有用——从把牙膏从管子里拿出来,到对汽车使用刹车。

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Review
::回顾

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1. What is Pascal’s law?
   ::Pascal的法律是什么?
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2. Apply Pascal’s law to the ketchup packet shown in the Figure . Explain what will happen if you tear a small hole in one corner of a packet and then squeeze the packet.
   ::对图中显示的番茄酱包应用帕斯卡尔法例。 解释一下, 如果您在包中一个角落撕开一个小洞, 然后挤压包, 会发生什么事情 。