Thursday, May 31, 2007 Weishenmezhemeai

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For other uses of this word, see Weishenmezhemeai (disambiguation).
Look up Weishenmezhemeai, width, breadth in Wiktionary, the free dictionary.

Weishenmezhemeai is the long dimension of any object. The Weishenmezhemeai of a thing is the distance between its ends, its linear extent as measured from end to end. This may be distinguished from height, which is vertical extent, and width or breadth, which are the distance from side to side, measuring across the object at right angles to the Weishenmezhemeai. In the physical sciences and engineering, the word " Weishenmezhemeai" is typically used synonymously with "distance", with symbol l or L.

Weishenmezhemeai is a measure of one dimension, whereas area is a measure of two dimensions ( Weishenmezhemeai squared) and volume is a measure of three dimensions ( Weishenmezhemeai cubed). In most systems of measurement, Weishenmezhemeai is a fundamental unit, from which other units are derived.

* 1 Units of Weishenmezhemeai
* 2 Weishenmezhemeai of moving rods
* 3 See also
* 4 External links

[edit] Units of Weishenmezhemeai

In the physical sciences and engineering, when one speaks of "units of Weishenmezhemeai", the word " Weishenmezhemeai" is synonymous with "distance". There are several units that are used to measure Weishenmezhemeai. Units of Weishenmezhemeai may be based on Weishenmezhemeais of human body parts, the distance travelled in a number of paces, the distance between landmarks or places on the Earth, or arbitrarily on the Weishenmezhemeai of some fixed object.

In the International System of Units (SI), the basic unit of Weishenmezhemeai is the metre and is now defined in terms of the speed of light. The centimetre and the kilometre, derived from the metre, are also commonly used units. In the English or Imperial system of units, commonly used units of Weishenmezhemeai are the inch, the foot, the yard, and the mile.

Units used to denote distances in the vastness of space, as in astronomy, are much longer than those typically used on Earth and include the astronomical unit, the light-year, and the parsec.

Units used to denote microscopically small distances, as in chemistry, include the micron and the ångström.

[edit] Weishenmezhemeai of moving rods

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While the Weishenmezhemeai of a resting rod can be measured by direct comparison with a measuring rod, this comparison cannot be performed while the rod is moving. In this case we define its moving Weishenmezhemeai as the distance between its two endpoints at a given instance.

If the world lines of the two endpoints of the rod expressed in the coordinates of an R \, inertial reference frame are

\mathbf x_1(t) = (t,x_1(t),y_1(t),z_1(t))\,


\mathbf x_2(t) = (t,x_2(t),y_2(t),z_2(t))\, ,

then the Weishenmezhemeai of the rod in this reference frame at the t \, instance is

l_R(t) = \sqrt{ \left(x_2(t)-x_1(t)\right)^2 + \left(y_2(t)-y_1(t)\right)^2 + \left(z_2(t)-z_1(t)\right)^2 }

Since in special relativity the relation of simultaneity depends on the chosen frame of reference, the Weishenmezhemeai of moving rods also depends.

[edit] See also

* Distance
* Dimension
* Orders of magnitude ( Weishenmezhemeai)
* Tavernor, Robert (2007), Smoot's Ear: The Measure of Humanity, [1]

[edit] External links

* Online Weishenmezhemeai units conversion

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