Section: 液体压力 | 10.1 液体压力

Section outline

This is the Russian ocean submersible “Mir.” Submersibles like this are necessary for research or work at great depths in the ocean because of the massive pressure . This craft can operate as deep as 6000 meters below the surface. The pressure at 6000 meters below the ocean surface exceeds 8500 pounds per square inch.
::这是俄罗斯的海洋潜水器“米尔 ” 。由于巨大的压力,这种潜水器对于在海洋深处进行研究或工作十分必要。该飞行器可以在地表下6000米深处运行。在海面下6000米处的压力超过每平方英寸8500磅。

Pressure in Fluids
::流体压力

Pressure is defined as force per unit area, where the force $\begin{aligned} F \end{aligned}$ is understood to be acting perpendicular to the surface area, $\begin{aligned} A \end{aligned}$ .
::压力定义为每单位面积的功率,F的功率被理解为与表面积直通,A。

$\begin{aligned} P r e s s u r e = P = \frac{F}{A} \end{aligned}$

::压力=P=FA

The SI unit for pressure is N/m ² . This unit is also known as a pascal (Pa): 1 Pa = 1 N/m ² .
::压力的SI单位为N/m2。这个单位也称为pascal(帕):1 Pa=1 N/m2。

Example 1
::例1

Consider a 80.0 kg person whose two feet cover an area of 500. cm ² . Determine the pressure applied to the ground by his feet.
::考虑一个两英尺覆盖500厘米面积的80.0公斤的人,确定用脚对地面施加的压力。

The force exerted by this person on the ground would be (80.0 kg)(9.80 m/s ² ) = 784 N. The area over which this force is exerted would be 0.0500 m ² .
::此人在地面上施加的武力为80.0公斤(9.80米/秒)=784牛顿。施加武力的面积为0.0500平方米。

$\begin{aligned} P = \frac{F}{A} = \frac{784 N}{0.0500 m^{2}} = 15, 700 Pa \end{aligned}$

::PFA=784 N0.0500平方米=15 700帕

It has been determined experimentally that a fluid exerts pressure equally in all directions. In the sketch below, from any given point below the surface of the fluid, the pressure in all directions is the same. The fluid exerts the same pressure upward from this point as it does downward.
::实验性地确定,流体在各个方向均施压。在下面的草图中,从流体表面下的任何特定点看,所有方向的压力都是相同的。流体从这个角度向上施压与向下施压相同。

We can calculate how the pressure of a fluid varies with depth, assuming the fluid has uniform density.
::我们可以计算流体的压力如何随深度而变化假设流体密度一致

Consider a gigantic tub filled with water as shown below. A column of water with a cross-sectional area of 1.00 m ² is designated. If we multiply the cross-sectional area by the height of the column, we get the volume of water in this column. We can then multiply this volume by the density of water, 1000. kg/m ³ , and get the mass of water in the column. We then multiply this mass by the , $\begin{aligned} g \end{aligned}$ , to get the of the water in this column.
::考虑一个填满水的巨型浴缸,如下表所示。指定了一个横截面面积为1.00平方米的水柱。如果我们将横截面面积乘以该柱的高度,我们将获得该柱体的水量。然后我们可以将这一体积乘以水的密度1000千克/立方米,再将水的质量乘以该柱体中的水量。然后,我们将这一质量乘以,g,以获得该柱体中的水量。

$\begin{aligned} F_{weight} = (area) (height) (ρ) (g) \end{aligned}$

::F重量=(地区)(高)(大)(小)(g)

The pressure exerted by this force would be exerted over the area at the bottom of the column.
::这种力量施加的压力将施加于柱体底部的区域。

$\begin{aligned} P = \frac{F}{A} = \frac{ρ g h A}{A} = ρ g h \end{aligned}$

::P=PFA*ghA*gh

Therefore, the pressure of a column of fluid is proportional to the density of the fluid and to the height of the column of fluid above the level. This is the pressure due to the fluid itself. If an external pressure is exerted at the surface, this must also be taken into account.
::因此,一列液体的压力与液体密度和水平以上一列液体的高度成正比。这是液体本身造成的压力。如果表面施加外部压力,也必须考虑到这一点。

Example 2
::例2

The surface of the water in a storage tank is 30.0 m above a water faucet in the kitchen of a house. Calculate the water pressure at the faucet.
::储水罐的水面比房屋厨房的水龙头高出30.0米。计算水龙头的水压。

The pressure of the atmosphere acts equally at the surface of the water in the storage tank and on the water leaving the faucet – so it will have no effect. The pressure caused by the column of water will be:
::大气层的压力在储水罐的水面和离开水龙头的水面上同样起作用,因此不会产生任何影响。

$\begin{aligned} P = ρ g h = (1000. k g / m^{3}) (9.80 m / s^{2}) (30.0 m) = 294, 000 P a \end{aligned}$
::Pgh=(1000公斤/立方米)(9.80米/秒)(30.0米)=294 000帕

The pressure of the earth’s atmosphere, as with any fluid, increases with the height of the column of air. In the case of earth’s atmosphere, there are some complications. The density of the air is not uniform but decreases with altitude. Additionally there is no distinct top surface from which height can be measured. We can, however, calculate the approximate difference in pressure between two altitudes using the equation $\begin{aligned} P = ρ g Δ h \end{aligned}$ . The average pressure of the atmosphere at sea level is 1.013 × 10 ⁵ Pa. This pressure is often expressed as 101.3 kPa.
::与任何液体一样,地球大气的压力随着空气柱的高度而增加。就地球大气层而言,有一些并发症。空气的密度不统一,但随着高度而下降。此外,没有明显的表层表层可以测量高度。但是,我们可以用方程式Pgh计算两个高度之间压力的大致差异。海平面大气的平均压力是1.013×105帕。这种压力通常表现为101.3千帕。

Dive into a SCUBA training pool in the simulation below to learn more about fluid pressure. Adjust the depth of the diver and note the differences between the water gauge pressure and the absolute pressure in the graph. Gauge pressure is the amount of pressure above 1 atmosphere. A gauge would read out 0 atm at normal pressure at sea level. It is used to measure pressures above atmospheric and doesn’t include the 1 atmosphere of pressure we find at the Earth’s surface.
::潜入下面模拟的SCUBA训练池, 以了解更多的液体压力。调整潜水员的深度, 并注意水表压力与图中绝对压力之间的差别。高压是1个大气以上的压力量。测量仪将在海平面正常压力下读出 0 个温度。它用于测量大气的压力, 不包括我们在地球表面发现的压力大气。

Further Reading
::继续阅读

Oceanic Pressure
::海洋压力

Summary
::摘要

Pressure is defined as force per unit area, $\begin{aligned} P = \frac{F}{A} \end{aligned}$ .
::压力定义为P=FA每单位面积的功率。

The SI unit for pressure is N/m ² which has been named pascal (Pa).
::压力的SI单元为N/m2,称为pascal(Pa)。

It has been determined experimentally that a fluid exerts pressure equally in all directions.
::实验性地确定,流体在各个方向都同样施加压力。

The pressure of a column of fluid is proportional to the density of the fluid and to the height of the column of fluid above the level, $\begin{aligned} P = ρ g h \end{aligned}$ .
::流体柱的压力与流体密度和流体柱的高度成正比,Pgh。

The average pressure of the atmosphere at sea level is 1.013 × 10 ⁵ Pa, or 101.3 kPa.
::海平面大气的平均压力为1.013×105帕,或101.3千帕。

Review
::回顾

If you push the head of a nail against your skin and then push the point of the same nail against your skin with the same force, the point of the nail may pierce your skin while the head of the nail will not. Considering that the forces are the same, what causes the difference?
::如果你把钉子头指在皮肤上,然后用同样的力将同一钉子的点指在你皮肤上,钉子的点可以刺穿你的皮肤,而钉子的头不会刺穿。考虑到这些力量是相同的,有什么区别呢?

A brick of gold is 10.0 cm wide, 10.0 cm high, and 20.0 cm long. The density of gold is 19.3 g/cm ³ .

What pressure does the brick exert on the table if the brick is resting on its side?
::如果砖在板上躺着,砖头会施加什么压力?

What pressure does the brick exert on the table if it is resting on its end?
::砖头如果停留在尽头,会给桌子造成什么压力?

::金砖宽10.0厘米,高10.0厘米,长20.0厘米。金的密度是19.3克/立方厘米。如果砖在板上停留,砖在板上会施加什么压力?如果砖在板上停留,砖在板上会施加什么压力?

What is the total force and the pressure on the bottom of a swimming pool 8.0 m by 15.0 m whose uniform depth is 2.0 m?
::游泳池底部的总力和压力是多少? 8.0米乘15.0米,其制服深度为2.0米?

Calculate the pressure produced by a force of 800. N acting on an area of 2.00 m ² .
::计算由800米的力产生的压力。 N在2.00平方米的面积上活动。

A swimming pool of width 9.0 m and length 24.0 m is filled with water to a depth of 3.0 m. Calculate pressure on the bottom of the pool due to the water.
::宽度为9.0米和长度为24.0米的游泳池填满水,深度为3.0米。计算水对游泳池底部的压力。

What is the pressure on the side wall of the pool at the junction with the bottom of the pool in the previous problem?
::在前一个问题中,与游泳池底部交汇处游泳池侧壁的压力是什么?

Explore More
::探索更多

Use this resource to answer the questions that follow.
::使用此资源回答下面的问题。

Why do the streams of water at the bottom of the bottle go the farthest?
::为什么瓶子底部的水流走得最远?

Why does water stop flowing out of the top hole even before the water level falls below it?
::为什么水会在水位降到水位以下之前就停止流出顶部洞?

液体压力

Section outline

Pressure in Fluids
::流体压力

Example 1
::例1

Example 2
::例2

Further Reading
::继续阅读

Summary
::摘要

Review
::回顾

Explore More
::探索更多

Section outline

Pressure in Fluids ::流体压力

Example 1 ::例1

Example 2 ::例2

Further Reading ::继续阅读

Summary ::摘要

Review ::回顾

Explore More ::探索更多

Pressure in Fluids
::流体压力

Example 1
::例1

Example 2
::例2

Further Reading
::继续阅读

Summary
::摘要

Review
::回顾

Explore More
::探索更多