Metrics system

The measurement system that uses such familiar units as feet, yards, ounces, pounds, and gallons is known as the English system. Another system of measurement, the metric system, will be en5 hasized in this chapter and subsequent chapters. The metric system of measurement is used almost exclusively in all 

Scientists measure many different quantities—length, volume, mass (weight), electric current, voltage, resistance, temperature, pressure, force, magnetic field intensity, radioactivity, and many others. The metric system and its recent extension, Systeme International d Unites (SI), were devised to make measurements and calculations as simple as possible. In this section, length, area, volume, and mass will be introduced. Temperature will be introduced in Sec. 2.7 and used extensively in Chap. 12. The quantities to be discussed here are presented in Table 2-1. Their units, abbreviations of the quantities and units, and the legal standards for the quantities are also included. 

Quantity Abbreviation Fundamental Unit Abbreviation of Unit Standard Comment 

The unit of length, or distance, is the meter. Originally conceived of as one ten-millionth of the distance from the north pole to the equator through Paris, the meter is more accurately defined as the distance between two scratches on a platinum-iridium bar kept in Paris. The U.S. standard is the distance between two scratches on a similar bar kept at the National Instimte of Standards and Technology. The meter is about 10% greater than the yard—39.37 in. to be more precise. 

Larger and smaller distances may be measured with units formed by the addition of prefixes to the word meter. The important metric prefixes are listed in Table 2-2. The most commonly used prefixes are kilo, milli. 

EXAMPLE 2.4. Since meter is abbreviated m (Table 2-1) and miUi is abbreviated m (Table 2-2), how can you tell the difference  

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Standard Practicefor Use ofi the International System ofiUnits (The Modernised Metric System), ASTM E380-93, ASTM, Philadelphia, Pa., 1993. 

NOTE Copyright SPE-AIME, The SI Metric System of Units and SFE s Tentative Mehic Standai d, Society of Petroleum Engineers, Dallas, 1977. 

Applicable dimensional units are shown individuaUy with each equation. The International Metric System (SI) is used when feasible otherwise commonly used U.S. engineering units are employed. The reader is referred to Sec. 1 for unit conversion fac tors. 

For the MKS (pure metric) system the following equation is used ... 

In the U.S., the result will be in inches for the metric system the results will be in meters. The relationship to convert between the two numbering system results is... 

In the metric system, pressure has a unit of newtons per square meter, which is called a pascal (Pa). Although the pascal is the scientific unit and is preferred, pounds per square inch (Ibs/iif) is comnion in the United States. For example, in most of Europe, tire pressure is recorded in pascals (typically 220,000 Pa), whereas tire pressure in American cars is measured in pounds per square inch (typically 32 Ibs/in ). As a point of reference, the pressure that the earth s... 

Metric Units of Measiu ement. For the purpose of this Code, metric units of measurement are in accordance with the modernized metric system known as the International System of Units (SI). 

The resistance when moving one layer of liquid over another is the basis for the laboratory method of measuring absolute viscosity. Poise viscosity is defined as the force (pounds) per unit of area, in square inches, required to move one parallel surface at a speed of one centimeter-per-second past another parallel surface when the two surfaces are separated by a fluid film one centimeter thick. Figure 40.16. In the metric system, force is expressed in dynes and area in square centimeters. Poise is also the ratio between the shearing stress and the rate of shear of the fluid. 

The concept of kinematic viscosity is the outgrowth of the use of a head of liquid to produce a flow through a capillary tube. The coefficient of absolute viscosity, when divided by the density of the liquid is called the kinematic viscosity. In the metric system, the unit of viscosity is called the stoke and it has the units of centimeters squared per second. One one-hundredth of a stoke is a centistoke. 

The English system of units is complicated compared to the metric system. In the English system, the units of mass are pounds-mass (Ibm) and the units of weight are pounds-force (Ibf). By definition, a weight (i.e., force) of one Ibf equals the force produced by one Ibm under the acceleration of gravity. Therefore, the constant, g, which has the same numerical value as g (32.17) and units of Ibm-ft/lbf-sec, is used in the definition of weight ... 

I am proud of this second edition. For one, I received input/feedback from our valued clients, industry FCC gurus, as well as my colleagues at RMS Engineering, Inc. Each chapter was reviewed carefully for accuracy and completeness. In several areas, 1 have provided additional discussions to cover different FCCU configurations and finally, both the metric and English units have been used to make it easier for readers who use the metric system. 

Data selected from Changing to the Metric System, Metals and Materials, Inst, of Metallurgists, 370, Dec. <1968). 

Scientific measurements are expressed in the metric system. As you know, this is a decimal-based system in which all of the units of a particular quantity are related to one another by factors of 10. The more common prefixes used to express these factors are listed in Table 1.2 (page 7). 

The standard unit of length in the metric system is the meter, which is a little larger than a yard. The meter was originally intended to be 1/40,000,000 of the earth s meridian that passes through Paris. It is now defined as the distance light travels in 1/299,792,458 of a second. 

In the metric system, mass is most commonly expressed in grams, kilograms, or milligrams ... 

Click Coached Problems for a self-study module on metric system prefixes. 

As you can see from this discussion, a wide number of different units can be used to express measured quantities in the metric system. Ibis proliferation of units has long been of concern to scientists. In 1960 a self-consistent set of metric units was proposed. This so-called International System of Units (SI) is discussed in Appendix 1. The SI units for the four quantities discussed are... 

The unit of land measure in the English system is the acre, while that in the metric system is the hectare. An acre is 4.356 X 104 ft2. A hectare is ten thousand square meters. The town of Willington in Connecticut requires a minimum area of 2.0 acres of land for a single-family dwelling. How many hectares are required ... 

A lap in most tracks that use the English system is 0.25 mi (English lap). In countries that use the metric system, a metric lap is 0.50 km. A champion marathon runner covers a mile in about 5.0 min. How many minutes will the runner take to run an English lap at that speed A metric lap ... 

Metric system A measuring system where all units of a particular type (e.g., volume) are related to one another by powers of ten, 6-7,9 Metric ton, 7 Microstates, 453... 

Decimals are used in the metric system. A decimal is a fraction in which the denominator is 10 or some power of 10. For example, 2110 (read as two tenths) is a fraction with a denominator of 10 1/100 (read as one one hundredth) is an example of a fraction with a denominator that is a power of 10 (ie, 100). 

The metric system uses decimals (or the decimal system). In the metric system, the gram is the unit of weight, the liter the unit of volume, and the meter the unit of lengtii. 

Display 3-1 lists the measurements used in the metric system. The abbreviations for the measurements are given in parentiieses. 

There are three systems of measurement of drug dosages die metric system, the apothecaries system, and household measurements. The metric system is die most commonly used system of measurement in medicine A physician may prescribe a drug dosage in die apotiiecaries system, but for die most part this ancient system of measurements is only occasionally used. The household system is rarely used in a hospital setting but may be used to measure drug dosses in the home... 

Fractions are not used in the metric system therefore, tiie fraction must be converted to a decimal by dividing tiie denominator into the numerator, or 3 -s- 5 = 0.6 or... 

Under certain circumstances, it may be necessary to compute an oral drug dosage because the dosage ordered by the physician may not be available, or the dosage may have been written in the apothecaries system and the drug or container label is in the metric system. 

Even if die physician s order was written in the apothecaries system, die drug container most likely would be labeled in die metric system. A conversion of apothecaries to metric will now be necessary because the drug label is written in die metric system. 

Conversion of units from one system to another is simply carried out if the quantities are expressed in terms of the fundamental units of mass, length, time, temperature. Typical conversion factors for the British and metric systems are ... 

The Systeme Internationa] (SI) is the internationally accepted form and elaboration of the metric system. It defines seven base units in terms of which all physical quantities can be expressed. At this stage all we need are ... 

SI (Systeme International) The International System of units a collection of definitions of units and symbols and their deployment. It is an extension and rational ization of the metric system. See also Appendix IB. side chain A hydrocarbon substituent on a hydrocarbon chain. 

Let s use the international metric system units for this calculation. In this system, the energy ( ) is given in joules (7). A Joule is the amount of work done that will produce the power of one watt continuously for one second. It is roughly the amount of energy required to lift one kilogram 10 centimeters. Mass (m) in the equation is in kilograms, and the speed of light (c) is in meters per second. 

Those familiar with the metric system should substitute kilograms for pounds in this example. 

In general, English units will be used throughout this book, with metric units given in parentheses. However, where metric units are the accepted practice, only these will be given. Only English units will be used in the examples, since the metric system has not yet been adopted by the chemical industry in the United States or Canada. 

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