Section outline

  • A silver sedan parked in a lot, illustrating vehicle maintenance discussion.


    Can you guess how old this car is?
    ::你能猜出这辆车多大吗?

    There are several benefits to maintaining the proper air pressure in a car tire. The ride is smoother and safer than with lowered pressure. The car gets better mileage and the tires don’t wear out as fast. The recommended pressure for that model of car (usually somewhere between 32-35 psi) is usually listed in the owner’s manual or stamped somewhere inside the door. The pressure on the tire is the maximum pressure for that tire, not the recommended one. Tire pressure is best measured when the tire is cold since driving the car for a while will up the air in the tire and increase the pressure.
    ::在汽车轮胎中保持适当的气压有若干好处。 车轮比降压更平滑、更安全。 汽车的里程会更好,轮胎不会耗尽得很快。 汽车的推荐压力(通常在32-35 psi之间)通常在车主手册中列出,或者在门内某处盖章。 轮胎的压力是轮胎的最大压力,而不是推荐的压力。 轮胎冷时,轮胎的压力是最好的测量,因为开一阵车会增加轮胎的空气并增加压力。

    Pressure Units and Conversion
    ::压力单位和转换

    A barometer measures by the height of the column of mercury. One unit of gas pressure is the millimeter of mercury (mmHg). An equivalent unit to the mmHg is called the torr, in honor of the inventor of the barometer, Evangelista Torricelli. The pascal (Pa) is the standard unit of pressure. A pascal is a very small amount of pressure, so the more useful unit for everyday gas pressures is the kilopascal (kPa). A kilopascal is equal to 1000 pascals. Another commonly used unit of pressure is the atmosphere (atm). Standard is called 1 atm of pressure and is equal to 760 mmHg and 101.3 kPa. Atmospheric pressure is also often stated as pounds/square inch (psi). The atmospheric pressure at sea level is 14.7 psi.
    ::气压单位是汞(mmHg)毫米; 与毫米Hg相当的单位称为托拉尔,这是气压计发明者Evangelista Torricelli的荣誉; 帕斯卡尔(Pa)是标准的压力单位; 帕斯卡尔(Pa)是很小的压力单位,因此,对日常气压而言,更有用的单位是千帕(kPa),千帕斯卡等于1000帕斯卡; 另一种常用的压力单位是大气(atm)。 标准称为1吨压力单位,相当于760毫米Hg和101.3千帕。 大气压力也常常以磅/平方英寸(psi)表示。 海平面大气压力为14.7皮西。

    1   atm = 760   mmHg = 760   torr = 101.3   KPa = 14.7   psi

    ::1 小时= 760 毫米Hg= 760 torr= 10.1.3 KPa= 14.7 psi

    It is important to be able to convert between different units of pressure. To do so, we will use the equivalent standard pressures shown above.
    ::重要的是能够在不同的压力单位之间转换。 为此,我们将使用上文显示的同等标准压力。

    Sample Problem: Pressure Unit Conversions
    ::问题:压力单位转换

    The atmospheric pressure in a mountainous location is measured to be 613 mmHg. What is this pressure in atm and in kPa?
    ::山区的大气压力测量为613毫米Hg。

    Step 1: List the known quantities and plan the problem.
    ::第1步:列出已知数量并规划问题。

    Known
    ::已知已知

    • given: 613 mmHg
      ::给出:613毫米Hg
    • 1 atm = 760 mmHg
      ::1 小时= 760毫米Hg
    • 101.3 kPa = 760 mmHg
      ::101.3千帕=760毫米Hg

    Unknown
    ::未知

    • pressure = ? atm
      ::压力=? 温度
    • pressure = ? kPa
      ::压力=? kPa

    Use conversion factors from the equivalent pressure units to convert from mmHg to atm and from mmHg to kPa.
    ::从等量压力单位转换成从毫米Hg转换成原子,从毫米Hg转换成千帕。

    Step 2: Solve.
    ::步骤2:解决。

    613   mmHg × 1   atm 760   mmHg = 0.807   atm 613   mmHg × 101.3   kPa 760   mmHg = 81.7   kPa

    ::613毫米Hgxx1在m760毫米Hg=0.807在m613毫米Hg×101.3千帕760毫米Hg=81.7千帕

    Step 3: Think about your result.
    ::步骤3:想想你的结果。

    The air pressure is about 80% that of standard atmospheric pressure at sea level. For significant figure purposes, the standard pressure of 760 mmHg has three .
    ::大气压力约为海平面标准大气压力的80%。

     

     

     

    Summary
    ::摘要

    • Calculations are described for converting between different pressure units.
      ::叙述不同的压力单位之间的换算。

    Review
    ::回顾

    1. What instrument measures gas pressure by the height of the column of mercury?
      ::哪些文书衡量汞柱高度的气体压力?
    2. 1 atm = ___ torr
      ::1时=______吨rr
    3. 32.02 atm = ___ kPa
      ::32.02 小时=______千帕
    4. 542 mmHg = ___ psi
      ::542毫米Hg = __ psi
    5. The pressure in a car tire is 35 psi. How many atmospheres is that?
      ::车胎的压力是35 psi 有多少大气?