Kilogram meter squared persecond squared11/11/2023 ![]() We can further simplify this factor if we use one of the many power of ten prefixes that are gathered in the table below. We may often be completely satisfied with the approximate relation 1 atm ≅ 1.0 x 10 5 Pa. This notation is also convenient for the (very common) situation where we do not need the full precision of the conversion factor. We humans like numbers that are smaller in magnitude (usually those in the 0.1 to 10.0 range feel most comfortable), and the familiar exponential power of ten notation is used to achieve that. The conversion factor above connecting two pressure units is not only a fairly long number, six digits, it is also a fairly large number. Conversion factors you have not memorized need to be looked up, and your text (and your exams) will contain all of them you'll need. Many common units have exact conversion factors, such as the length conversion 1 ft = 12 in, which is one you probably know. The final two areas we cover here concern the common "power of ten prefixes" that are used to express quantities that may vary over wide magnitudes and the approach we take to convert from one unit to another.įor example, our common pressure unit of atmosphere is related to the fundamental SI pascal unit as follows: 1 atm = 101,325 Pa (exactly). But no matter which unit is used to express a pressure, they are all decomposable into kg m –1 s –2 base units. There are several other units used to express pressure, such as the atmosphere (abbreviated atm), the bar, and the torr (abbreviated Torr after Evangelista Torricelli). Pressure is a force per unit area, and if you recall Newton's law that force is mass times acceleration, you can see that pressure is kg m –1 s –2. The second composite quantity we will use often is pressure, and the fundamental composite SI unit for pressure is the pascal, or Pa (named after Blaise Pascal). Likewise, the temperature unit, kelvin, is not capitalized while the symbol, K, is.)Įnergy can be decomposed into the following set of base units: kg m 2 s –2 or "kilogram meter squared per second squared." If you recall the elementary equation that states kinetic energy is mass times speed squared (and speed is length per unit time), you can see the source of this decomposition. (Note that the symbol is capitalized, but the name, joule, isn't, even though it is named after James Joule. In addition to these base units, we will often encounter units for important physical quantities such as pressure and energy that are given a single name but which are quantities that are composite combinations of the fundamental units.įor example, the common unit of energy we will use is the joule, symbolized J. The seventh, luminous intensity, is fairly obscure and won't interest us. Here they are, but only the first six (in bold) will interest us in Chem 5 and 6. ![]() The metric system (officially known as the SI system, for " Le Système International d'Unités") has seven fundamental or base quantities. The value of any physical quantity (such as 5.75 ft) is the product of a numerical value (5.75) and a unit (ft). This brings us to our first and most important rule:Īlways write the units associated with any physical quantity. The unit specifier makes all the difference, and without it, the pure number itself is meaningless. Thus, one physical quantity can often be expressed with different units, and it is completely correct to write 5.75 ft = 1.7526 m even though 5.75 ≠ 1.7526. This is equivalent to 5.75 ft, of course, and in the system of units used in the rest of the world (as well as in Chemistry 5 and 6), this same height is 1.7526 m, using the metric system's basic length unit, the meter. ![]() For example, a person's height may be expressed in the common American units of length, feet and inches, as 5 ft 9 in. Physical quantities often (in fact, almost always) are expressed in terms of a certain number of characteristic units of measure representing the physical quantity itself. ![]() Type in unit symbols, abbreviations, or full names for units of length, area, mass, pressure, and other types.General Chemistry: Dimensional Analysis and Units You can find metric conversion tables for SI units, as well as English units, currency, and other data. It is abbreviated m².Ĭ provides an online conversion calculator for all types of measurement units. Square metre to kilo/square meter, or enter any two units below: Enter two units to convert From:Ī square metre (US spelling: square meter) is by definition the area enclosed by a square with sides each 1 metre long. You can do the reverse unit conversion from
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