Length metric system

In the metric system lengths are calculated in meters, masses are calculated in grams, and volumes are calculated in liters. The prefix of each unit is very important. You should be familiar with the following prefixes ... 

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. 

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 ... 

Scientists measure many different quantities—length, volume, mass (weight), electric current, 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 chapter, length, area, volume, and mass will be introduced. Temperature will be introduced in Sec. 2.7 and used extensively in Chap. 11. 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. 

In the metric system, the three primary or fundamental units are the meter for length, the liter for volume, and the gram for weight. In addition to these... 

The system of units used in chemistry is the SI system (Systeme International), which is related to the metric system. There are base units for length, mass, etc. and decimal prefixes that modify the base unit. Since most of us do not tend to think in these units, it is important to be able to convert back and forth from the English system to the SI system. These three conversions are useful ones, although knowing the others might allow you to simplify your calculations ... 

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

You measure a length to be 0.005 m. How can this be better expressed using a metric system prefix ... 

The metric system, or Systeme International d Unites (SI system as it is commonly known), is the predominant system of measurement in the world. In fact, the United States is one of only about three countries that do not commonly use the metric system. The metric system attempts to eliminate odd and often difircult-to-remember conversions for measurements (5,280 feet in a mile, for example). It is a decimal-based system with standard terminology for measurements of length, volume, and mass (weight). It also uses standard prefixes to measure multiples of the standard units. 

In 1960 the International General Conference on Weights and Measures adopted an improved form of the metric system, The International System of Units (SI). The units of mass, length, and time are the kilogram (kg), meter (m), and second (s). The following prefixes are used for fractions and multiples ... 

Under an international agreement concluded in 1960, scientists throughout the world now use the International System of Units for measurement, abbreviated SI for the French Systeme Internationale d Unites. Based on the metric system, which is used in all industrialized countries of the world except the United States, the SI system has seven fundamental units (Table 1.3). These seven fundamental units, along with others derived from them, suffice for all scientific measurements. We ll look at three of the most common units in this chapter—those for mass, length, and temperature—and will discuss others as the need arises in later chapters. 

The metric system consists of a base unit and (sometimes) a prefix multiplier. Most scientists and healthcare providers use the metric system, and you are probably familiar with the common base units and prefix multipliers. The base units describe the type of quantity measured length, mass, or time. The SI system is sometimes called the MKS (meter, kilogram, second) system, because these are the standard units of length, mass, and time upon which derived quantities, such as energy, pressure, and force, are based. An older system is called the CGS (centimeter, gram, second) system. The derived CGS units are becoming extinct. Therefore, we will focus on the MKS units. 

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 measures of length, volume, mass, energy, and temperature are used to evaluate our physical and chemical environment. Table 2.2 compares the metric system with the more recently accepted SI system (International System of Units). The laboratory equipment associated with obtaining these measures is also listed. 

On the eve of the French Revolution, June 19, 1791, King Louis XVI of France gave his approval of the system. The next day, Louis tried to escape France but was arrested and jailed. A year later from his jail cell, Louis directed two engineers to make the measurements necessary to implement the metric system. Because of the French Revolution, it took six years to complete the required measurements. Finally, in June 1799 the Commission sur l unite de poids du Systeme Metrique decimal met and adopted the metric system. It was based on the gram as the unit of weight and the meter as the unit of length. All other measurements were to be derived from these units. The metric system was adopted For all people, for all time. ... 

Temperature. Temperature was not one of the original properties that the French academy deemed necessary to include in the metric system. In fact, as late as 1921, members of the 6th General Conference of the International System of Weights and Measures were still objecting to the inclusion of measurements (other than length and mass) seemingly for no other reason other than to keep the base units pure. ... 

The original idea of the metric system was that either approach would provide the same unit of metric volume. Unfortunately, it did not work because of the subtle differences in density caused by subtle differences in temperature. Thus, the kilogram-based milliliter equaled 1.000,027 cubic centimeters. Because of the discrepancy, the International System for Weights and Measures had to make a choice between which approach would be accepted to obtain volume measurements, and the nod was eventually given to the cubic length technique. The use of liters and milliliters in volumetric ware is therefore misleading because the unit of volume measurement should be cubic meters (cubic centimeters are used as a convenience for smaller containers). The International System of Units (SI) and the ASTM accept the use of liters and milliliters in their reports, provided that the precision of the material does not warrant cubic centimeters. Because the actual difference in one cubic centimeter is less than 3 parts in 100,000, for most work it is safe to assume that 1 cm3 is equal to 1 mL. 

The name SI is derived from Systbme International d Unites and has evolved from an original basis of a given length (meter) and mass (kilogram) established by members of the Paris Academy of Science in the late eighteenth century. The original system was known as the metric system, but there are differences in the modem SI system and the old metric system based primarily on new names being added for derived terms. 

The meter is the primary unit of length in the metric system. Its abbreviation is m. The meter is defined in such a way that it can be duplicated precisely in any well-equipped laboratory in the world. It had been defined as the distance between two marks on a metal bar kept at the Bureau of Weights and Measures in Paris. (It now has an even more precise definition.) A meter is 39.37 in. long—3.37 in. longer than a yard. 

The metric system and its newer counterpart, SI, use subunits and multiples of units that are equal to powers of 10, and they also use the same prefixes to mean certain fractions or multiples, no matter what primary unit is being modified. The meter is the primary unit of length the gram is the primary unit of mass and the liter (the cubic meter in SI) is the primary unit of volume. The prefixes centi-(0.01), (0.001), and kilo (1000) are used with any of... 

The relationships between the customary units are not as systematic as the relationships between units in the metric system. Here, lengths are measured in inches, feet, yards, and miles. Weights are measured in pounds and ounces. And volumes are measured in cubic inches, cubic feet, and so forth. Below is a chart of common conversions for customary units. 

The base units of the American engineering system are the foot (ft) for length, the pound-mass (Ibm) for mass, and the second (s) for time. This system has two principal difficulties. The first is the occurrence of conversion factors (such as 1 ft/12 in), which, unlike those in the metric systems, ate not multiples of 10 the second, which has to do with the unit of force, is discussed in the next section. 

According to Newton s second law of motion, force is proportional to the product of mass and acceleration (length/time ). Natural force units are, therefore, kg-m/s (SI), g-cm/s (CGS), and lbm-ft/s (American engineering). To avoid having to carry around these complex units in all calculations involving forces, derived force units have been defined in each system. In the metric systems, the derived force units (the newton in SI, the dyne in the CGS system) are defined to equal the natural units ... 

The metric system of measurement is an internationally agreed-upon set of units for expressing the amounts of various quantities such as length, mass, time, temperature, and so on. 

Because of its convenience and consistency, scientists have used the metric system of units for more than 200 years. Originally, the metric system was based on only three fundamental units the meter for length, the kilogram for mass, and the second for time. Today, there are more than 50 officially recognized SI units for various scientific quantities. 

Time The SI base unit for time is the second (s). The frequency of microwave radiation given off by a cesium-133 atom is the physical standard used to establish the length of a second. Cesium clocks are more reliable than the clocks and stopwatches that you use to measure time. For ordinary tasks, a second is a short amount of time. Many chemical reactions take place in less than a second. To better describe the range of possible measurements, scientists add prefixes to the base units. This task is made easier because the metric system is a decimal system. The prefixes in Table 2-2 are based on multiples, or factors, of ten. These prefixes can be used with all SI units. In Section 2.2, you will learn to express quantities such as 0.000 000 015 s in scientific notation, which also is based on multiples of ten. 

Recall from Chapter 2 that the universal unit system used hy scientists is called Le Systeme Internationale d Unit6s or SI. It is a metric system based on seven base units—meter, second, kilogram, kelvin, mole, ampere, and candela—from which all other units are derived. The size of a unit in a metric system is indicated by a prefix related to the difference between that unit and the base unit. For example, the base unit for length in the metric system is the meter. One tenth of a meter is a decimeter where the prefix deci- means one tenth. And, one thousand meters is a kilometer. The prefix kilo- means one thousand. 

Traditionally, measurements in the clinical laboratory have been made in metric units. In the early development of the metric system, units were referenced to length, mass, and time. The first absolute systems were based on the centimeter, gram, and second (CGS) and then the meter, kilogram, and second (MKS). The SI is a different system that was accepted internationally in 1960. The units of the system are called SI units. 

Scientists use the metric system to measure distance and length. They measure distance and length using a metric ruler, tape measure, or other special tools. A meter is a specific unit of measurement. A meter can be broken down into smaller parts called centimeters and millimeters. There are 100... 

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. 

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