Inch, English system

Meter a unit of measurement of length in the metric system. One meter equals approximately 39.37 inches in the English system. 

The common unit of measurement for natural gas is the standard cubic foot in the English system and the standard cubic meter in the metric system. Each of these standards is expressed at pressures and temperatures commonly used as standard to the system in the geographical area of concern. In the United States, where standards frequently vary from state to state, the cubic foot is frequently expressed in the English system at standard conditions of 14.73 pounds per square inch absolute (psia) and 60 degrees Fahrenheit (60°F), although there are a number... 

Quantitative calculations and qualitative interpretations are fundamental to fully grasp the concepts of chemistry. Quantitative values must include a number and a unit. Two common units of measurement are the conventional (English) system and the metric system. The conventional set of units includes inches, feet, miles, gallons, and pounds. These units, although common in the United States, are not used in science or by most of the world. However, the metric system is becoming more common in the United States. The metric system s base-10 units are easier to use and essential for scientific calculations. However, because most readers of this book are more familiar with the conventional system, it will be necessary to convert to and from the metric system. 

The meter is the standard unit of length (distance) in both SI and metric systems. The meter is defined as the distance light travels in a vacuum in 1/299,792,468 second. It is approximately 39.37 inches. In situations in which the English system would use inches, the metric centimeter (1/100 meter) is convenient. The relationship between inches and centimeters is shown in Figure 1-12. 

The same prefixes are used with mass as with distance, and they have the same meanings. That is one facet that makes the metric system so easy. In the English system, the subdivisions of a yard are a foot—one-third of a yard—and an inch—one-thirty-sixth of a yard. The subdivision of an Avoirdupois pound is an ounce, one-sixteenth of a pound. The subdivision of a Troy pound is an ounce, one-twelfth of that pound. (Gold and silver are measured in Troy ounces.) Each type of measurement has a different subdivision, and none is a multiple of 10. The metric system uses the same prefixes for all types of measurements, they are all multiples of 10, and they always mean the same thing. The symbols for the units and prefixes are easier to learn than those for the English system units. For example, pound is abbreviated lb and ounce is oz, whereas the metric prefixes are almost always closely related to their names. It is easier to convert metric measurements because the prefixes mean some multiple of 10 times the fundamental unit. 

The English system equivalent is a pressure of 14.7 Ib/in (poimds per square inch) or 29.9 in Hg (inches of mercury). A recommended, yet less frequently used, systematic unit is the pascal (or kUopascal), named in honor of Blaise Pascal, a seventeenth-century French mathematician and scientist ... 

Note Throughout the book we have vacillated between the metric and English systems, especially for dimensions. At first, we wished to be consistent, but this was not practical because of the wide variation in dimensions from smaU-pitch devices to large circuit boards. Thus, mils, micrometers, and nanometers are used for the smallest dimensions while inches or millimeters are used for the large dimensions. For convenience, conversion tables are provided in the Appendix. 

Conversion factors for some of the English system units commonly used in the United States for nonscientific measurements (for example, powds and inches) are provided inside the back cover of this book. 

Since the English System was used in the United States for many years with units of inches, feet, yards, miles, cups, quarts, gallons, etc., many people were not comfortable with the metric system until recently. Most students wonder why they ever preferred the older system, when they discovered how easy it is to multiply metric units. 

The two most common unit systems are the English system, used in the United States, and the metric system, used in most of the rest of the world. The English system uses imits such as inches, yards, and pounds, while the metric system uses centimeters, meters, and kilograms. The most convenient system for science measmements is based on the metric system and is called the International System of units or SI units. SI units are a set of standard units agreed on by scientists throughout the world. 

The units of pressure are those of force per unit area. In the English system, these are pounds per square inch (Ib/in. ), often abbreviated as psi and in the metric system, these are newtons per square meter (N/m ), also called a pascal (Pa). Several other units of pressure are also in common use (Table 11-1). 

Chemistry and physics are experimental sciences, based on measurements. Our characterization of molecules (and of everything else in the universe) rests on observable physical quantities, expressed in units that ideally would be precise, convenient and reproducible. These three requirements have always produced trade-offs. For example, the English unit of length inch was defined to be the length of three barleycorns laid end to end—a convenient and somewhat reproducible standard for an agricultural society. When the metric system was developed in the 1790s, the meter was defined to be... 

The pressure P of a fluid on a surface is defined as the normal force exerted by the fluid per unit area of the surface. If force is measured in N and area in m2, the unit is the newton per square meter or N nTJ, called the pascal, symbol Pa, the basic SI unit of pressure. In the English engineering system the most common unit is the pound force per square inch (psi). 

Napoleon s armies spread the system throughout continental Europe, but the British (and consequently the Americans) hung to the old English inch-pound-second system. From cgs the kilogram-meter-second (mks) system evolved, and finally SI (Systeme International d Unites) was bom from mks with the addition of units of current (ampere), temperature (kelvin), and brightness (candela). The International Temperature Scale is defined by 13.8033 K (triple point of equilibrium H2) 24.5561 K (triple point of Ne) and 1234.93 K (freezing temperature of Ag). 

The question mark stands for the number we want to find. To solve this problem, we must know the relationship between inches and centimeters. In Table 2.7, which gives several equivalents between the English and metric systems, we find the relationship... 

Length The basic unit of length in the SI system is the meter (m). A meter is a little longer than a yard 1.094 yards eire in a meter. The most useful Sl/English conversion for length is 2.54 centimeters = 1 inch... 

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