Meter, kilogram, and second

Dimensional calculations are greatly simplified if a consistent set of units is employed. The three major reference dimensions for mechanics are length, mass, and time, but length can be measured in units of inches, feet, centimeters, meters, etc. Which should be used The scientific community has made considerable progress toward a common system of reference units. This system is known as SI from the French name Systeme International d Unites. In SI, the reference units for length, mass, and time are the meter, kilogram, and second, with symbols m, kg, and s, respectively. 

The International System of Units is founded on seven base quantities (Table 3.1) that cover the whole field of natural science. Again, the system of quantities and equations of mechanics rests on the three base quantities length, mass and time, for which the units meter, kilogram and second are now internationally accepted. The derived unit of force is the Newton (N), being the force that gives the unit mass (kg) a unit acceleration (1 m s-2). The derived unit of energy is the Newton meter (N m). 

Units. Labels which distinguish one type of measurable quantity from other types. Length, mass and time are distinctly different physical quantities, and therefore have different unit names, meters, kilograms and seconds. We use several systems of units, including the metric (SI) units, the English (orU.S. customary units), and a number of others of mainly historical interest. 

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. 

The metric system was modified as Systeme International (SI) units (Table 1.6) to prevent some confusion. The SI is based on seven fundamental units—including the mole, meter, kilogram, and second—from which the others are derived. The significant changes for soil chemistry are mole of ion charge for equivalent, siemens for mho, joule for calorie, and pascal for pressure. Table 1.4 summarizes the SI units most frequently encountered in sod chemistry. SI allows easier conversion and communication between disciplines, but unfortunately discards some useful and familiar units, such as angstrom and equivalent,... 

MKS system n. A system of units derived from the meter, kilogram, and second. Now superceded for scientific purposes by the SI units, which are based on the MKS system. 

Two traditional selections of a basic unit for mass, length, and time are often encountered. The mks form uses meters, kilograms, and seconds. The mks energy unit, called the joule... 

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 ... 

The SI is constructed from seven base units for independent quantities (ampere, candela, kelvin, kilogram, meter, mole, and second) plus two supplementary units for plane and solid angles (radian and steradian). Most physicochemical measurements can be expressed in terms of these units. 

FIG. 5-29 Hi correlation for various packings (Table 5-28-G). To convert meters to feet, multiply by 3.281 to convert pounds per hour-square foot to kilograms per second-square meter, multiply by 0.001.356 and to convert millimeters to inches, multiply by 0.0.394. [Bolles and Fair, Inst. Chem. Eng. Symp. Ser., no.. 56, 3,3/35 (1.96.9).]... 

NOTE AU groups are dimensionless. To convert dynes per square centimeter to joules per square meter, miJtiply by 10" to convert poises to newton-seconds per square meter, multiply by 10" to convert feet per second to meters per second, multiply by 0.3048 to convert feet to meters, multiply by 0.3048 to convert pounds per minute-foot to kilograms per second-meter, multiply by 0.025 to convert pounds per cubic foot to kilograms per cubic meter, multiply by 16.019 to convert pounds per minute squared to kilograms per second squared, multiply by 1.26 X lO"" to convert British thermal units per hour to kilojoules per second, multiply by 2.63 X lO"" and to convert British thermal units per hour-square foot-degree Fahrenheit per foot to joules per square meter-second-kelvin per meter, multiply by 1.7307. 

FIG. 14-53 Pressure for metal Intalox saddles, sizes No, 25 (nominal 25 mm) and No, 50 (nominal 50 mm). Air-water system at atmospheric pressure, 760-mm (30-in) column, hed height, 3,05 m (10 ft), L = liquid rate, kg/(s-m ). To convert kilograms per second-square meter to pounds per hour-square foot, multiply hy 151,7 to convert pascals per meter to inches of water per foot, multiply hy 0,1225, (Coutiesy Notion Company, Akron, Ohio.)... 

FIG. 14-54 Pressure drop for Flexipac packing, sizes No, 1 and No.. 3, Air-water system at atmospheric pressure. Liquid rate in gallons per minute-square foot. To convert (feet per second) (younds per cubic foot) " to (meters per second) (kilograms per cubic meter) " , multiply by 1,2199 to convert gallons per minute-square foot to pounds per hour-square foot, multiply by 500 to convert inches of water per foot to millimeters of water per meter, multiply by 83,31 and to convert pounds per hour-square foot to kilograms per second-square meter, multiply by 0,001.356, Coutiesy Koch Engineering Co., Wichita, Kansas.)... 

FIG. 14-61 Liq uid distribution in a 6-in column packed with 1/4-in broken-stone packing. Increments of radius represent equal-annual-area segments of tower cross section. Central-point inlet. Water rate = 500 lb/(b-fr). Air rate = 810 lb/(b-ft ). To convert pounds per bour-square foot to kilograms per second-square meter, multiply by 0.00L356 to convert inches to centimeters, multiply by 2.54. (Data from Baker, Chilton, and Vernon, in Shetxuood and Pigford, Absorption and Extraction, 2d ed., McGraw-Hill, New York, 1952. )... 

FIG, 14-77 Mass-transfer coefficients versus average gas velocity—HCl absorption, wetted-wall column. To convert pound-moles per hour-square foot-atmosphere to Idlogram-moles per second-square meter-atmosphere, multiply by 0.00136 to convert pounds per hour-square foot to kilograms per second-square meter, multiply by 0.00136 to convert feet to meters, multiply by 0.305 and to convert inches to milhmeters, multiply by 25.4. [Dohratz et at, Chem. Eng. Prog., 49, 611 (1953).]... 

To convert gallons per hour to liters per second, multiply hy 0.00105 to convert tons per hour to kilograms per second, multiply hy 0.253 and to convert cubic feet to cubic meters, multiply hy 0.0283. 

NOTE To convert cubic feet to cubic meters, multiply by 0.028.32 to convert horsepower to kilowatts, multiply by 0.7457 to convert pounds per cubic foot to kilograms per cubic meter, multiply by 16.02 to convert tons per hour to kilograms per second, multiply by 0.252 to convert revolutions per minute to radians per second, multiply by 0.1047 to convert pounds per minute to kilograms per minute, multiply by 0.45 15 and to convert horsepower per ton to kilowatts per metric ton, multiply by 0.8. 152. 

FIG. 29-60 Excess head developed by lean and semilean pumps and the steam-throttle flow for a semdean-pump turbine. To convert gallons per minute to cubic meters per minute, multiply by 0.00379 to convert pounds per hour to kilograms per second, multiply by 1.260 X 10 . ... 

Two systems of units are in common usage in mechanics. The first, the SI system, is an absolute system based on the fundamental quantities of space, time, and mass. All other quantities, including force, are derived. In the SI system the basic unit of mass is the kilogram (kg), the basic unit of length (space) is the meter (m), and the basic unit of time is tbe second (s). The derived unit of force is the Newton (N), which is defined as the force required to accelerate a mass of 1 kg at a rate of 1 m/s-. 

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. 

SI Units—The International System of Units as defined by the General Conference of Weights and Measures in 1960. These units are generally based on the meter/kilogram/second units, with special quantities for radiation including the becquerel, gray, and sievert. 

Contacting power is variously expressed in units of MJ/1000 m3 (SI), kWh/1000 m3 (meter-kilogram-second system), and hp/(1000 ft3/min) (U.S. customary). Relationships for conversion to SI units are... 

There is often some confusion between the terms standards and reference materials. Primary standards represent the top-tier of chemical standards and, in principle, provide a means of establishing the traceability of analytical data to the SI measurement units (e.g., the kilogram, mole, meter, and second). A limited number of pure chemicals are recognized as primary standards (and thus can constitute certified reference materials). Most certified reference materials are not of themselves primary standards rather, the property values assigned to them are traceable to primary standards where practical. 

In the present book, for magnetism we use the SI unit that is based on the MKS A (meter, kilogram, second, ampere) system. In accordance with that, the tesla (1T = 10" gauss) was presented as the magnetic unit in Chapter 17 (see Fig. 17.10a and b). It is useful to know both the SI and Gaussian systems and be able to convert between them. Thus, when one attempts to solve a magnetics problem, to avoid errors one is well advised to stick to a single convenient unit system. A useful conversion table of... 

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