Name: si and customary measurement systems
Uploaded: 2023-09-22T11:49:19.000Z
Duration: 1 min 27 s
Channel: JoVE

长度、质量和时间是测量的基本物理量，它们的单位被称为基本单位。
由基本单位导出的单位称为导出单位。
单位制可分为国际单位制（SI单位）和美国 customary 单位制。
在国际单位制（SI）中，米、千克和秒是基本单位，而在美国 customary 单位制中，英尺、磅和秒是基本单位。
例如，力的国际单位制（SI）单位是牛顿，它是一个导出单位。&#160; 其定义为使一千克质量产生一米每二次方秒加速度所需的力。
在美制单位体系中，质量的单位是斯勒格（slug），这是一个导出单位。它被定义为：当受到一磅力作用时，产生每秒平方一英尺加速度的物质量。
可以使用换算系数将一个系统的单位转换为另一个系统的单位。

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	<li>希伯勒，RC（2016 年）。工程力学 \u2012 静力学和动力学。 新泽西州霍博肯:Pearson Prentice Hall。第 7\u20128 页</li>
	<li>比尔，F.P.;约翰斯顿，ER;马祖克，DF;克伦威尔，PJ 和塞尔夫，BP（2019 年）。工程师的矢量力学 \u2012 静力学和动力学。纽约:麦格劳-希尔。第 4 页和第 8 页</li>
	<li>梅里亚姆，JL;Kraige， LG 和 Bolton， JN （2020）。工程力学 \u2012 静力学。新泽西州霍博肯:约翰·威利。第 7 页和第 8 页</li>
</ol>

计量单位

Units of Measurement

机械工程是工程学最古老的分支之一，涉及设计、分析以及制造机器和机械系统。计量单位的使用可以确保机械工程计算的精确性，提供用于表达和比较物理量的标准系统。 历史上存在多种计量系统，例如巴比伦系统、罗马系统、埃及系统、奥林匹克系统、英制系统和印度河谷系统。 国际单位制(SI）是现代机械工程学科通用的计量标准。它基于一些基本的单位，对其进行组合来表示其他物理量。 从基本单位派生得到的单位被称为派生单位。例如，力的SI单位是牛顿，这是一个派生单位。它被定义为一千克的质量以一秒的每二次方米的速率来加速其所需的力。 世界各地使用着不同的计量单位。除了国际单位制（SI）之外，美国单位制度也是常用的计量单位之一。在美国常用的计量单位中，基本单位是英尺、磅和秒。其中长度的单位是英尺，质量的单位是磅，时间的单位是秒。 在美国常用的计量单位中，质量的单位是slug，这是一个派生单位。它定义为当受到一磅力的作用时，由一英尺每二次方秒加速度运动所需的质量。 由于许多国家仍采用美国的常用计量单位制度，因此也建立了各种单位之间的换算关系。例如，一米等于3.28英尺。派生单位也会因为标准不同而有所差异。例如，SI系统使用牛顿作为力的单位，而美国的常用单位则是磅。 计量单位在机械工程中非常重要，因为对物体进行精确的测量离不开这些计量单位。工程师使用这些单位来设计和分析机器和机械系统，从而估算机械部件的负载、应力和变形，以此来预测机器在不同工作条件下的行为。

机械工程是工程学最古老的分支之一。它涉及机器和机械的设计、分析与制造……

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si and customary measurement systems

Mechanical engineering depends on units of measurement for precise and accurate calculations. These units give engineers a standard way to express and compare physical quantities. They are essential when designing and analyzing machines and mechanical systems.

Many historical measurement systems have been used over time. Examples include the Babylonian system, the Roman system, the Egyptian system, the Olympian system, the British system, and the Indus Valley system. Today, the International System of Units, or SI, is the widely recognized standard used in mechanical engineering.

The SI system is built from base units. These base units can be combined to describe other physical quantities, which are called derived units. For example, the SI unit of force is the Newton. One Newton is the force needed to accelerate one kilogram of mass at one meter per second squared.

Another common system is the U.S. Customary System of Units. Its base units are the foot, the pound, and the second. In this system, length is measured in feet, mass is measured in pounds, and time is measured in seconds. The slug is the derived unit used for mass in this system, and it is defined by the amount of matter accelerated by one foot per second squared under a force of one pound.

Because many countries still use the U.S. Customary System, conversion relationships are important. For example, one meter equals 3,280 feet. Derived units also differ between systems. SI uses the Newton for force, while the U.S. Customary System uses the pound. Engineers use these units to estimate loads, stresses, and deformations, and to predict how machines behave under different operating conditions.

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Mechanical engineering depends on units of measurement for precise and accurate calculations. These units give engineers a standard way to express and compare physical quantities. They are essential when designing and analyzing machines and mechanical systems. Many historical measurement systems have been used over time. Examples include the Babylonian system, the Roman system, the Egyptian system, the Olympian system, the British system, and the Indus Valley system. Today, the International...

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Explore SI and U.S. Customary units, base and derived units, and how engineers use measurement systems to calculate force, loads, and machine behavior.

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SI and Customary Measurement Systems

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