Metric units of length review (mm, cm, m, & km)
Mar 23, · Welcome to how to Convert Metric Units of Length with Mr. J! Need help with mm, cm, m, and km conversions? You're in the right place!Whether you're just star. Whether you're just starting out, or need a quick refresher, this is the video for you if you need help with converting metric units of length. Mr. J will go through the following conversions step by step for millimeters, centimeters, meters, and kilometers: convert mm to cm-convert cm to mm-convert cm to m-convert m to cm-convert km to m.
This is a convenient online ruler that could be calibrated to actual sizemeasurements in cm, mm and inch, the upper half is the millimeter ruler and centimeter ruler, the lower half is an inch ruler. In order to accurately measure the length of your item, we strongly recommend that you calibrate this online ruler first, set the correct pixels per inch to your own device, after adjustment, you will have the most precise ruler online.
Save the pixels per inch PPI according your own device, then you can use this ruler next time. Pixels per inch :show ruler adjuster. Dragging ruler adjuster left or right to fit the size of your reference object, remember to save the setting for the next time you use it, after save the setting, refresh your brower to check the result. On the most popular browsers you can press the F5 key or click on the refresh button.
We hope to provide a more user-friendly experience, are you willing to offer a native language version for your country? We are looking for volunteer to improve the content in your native language, if you are interested to help this, please visit this translation page.
Below are some other language version. One day, i took my laptop computer to work in the coffee shop, just what does the word alluvial mean a project on hand, and i had to tell the customer the actual size of a product.
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This ruler measure in two different units of length, inches on one side English ruler and centimeters on the other side metric ruler. A metric ruler is use to measure centimeter cm and millimeter mmthe centimeter is a unit of length in the International System of Units; An English ruler provides incremental measurements in inches, with each inch further divided into smaller fractions. Read an English ruler using fractions of an inch.
The distance between any two large numbered lines is 1 inch. Observe the much simpler metric rulers. The distance between any two large numbered lines is 1 cm, a william shakespeare what else did he write ruler features two types of lines. The largest mark centimeters, or cm.
The smallest lines mark millimeters, or mm. The measurements are decimalized and there are no fractions. Record distances by the name of the line that it most closely matches. This page is a darknet that can't be found on Google, add it to your bookmark, favorites, otherwise you will lose it.
To have the most accurate ruler online, just set the pixels per inch PPIbelow are some ways to know the pixels per inch to your device.
Turn your smartphone and tablet to a ruler and measure the scale of any small thing. Scan above QR code to open browser, what is a steam boiler turn your mobile phone screen to landscape mode, so that the length of online ruler will longer.
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Objective: I know how to convert between different metric measurements. Metric measurements of length are millimeter (mm), centimeter (cm), meter (m), kilometer (km). 10 mm = 1 cm cm = 1 m m = 1 km. Example (a) Change km to m (b) Change 54mm to cm. Solution: (a) km= xm = m (b) 54mm = cm = cm. Mar 17, · Understand the Sizes of millimeters, centimeters, meters, and kilometers#Math #Metric #Length #Measurement #Data #Meters #Kilometers #Centimeters #Millimeter. 1 m = 1,, ?m: millimeters: mm: Metric System: 1 m = 1, mm: centimeters: cm: Metric System: 1 m = cm: decimeters: dm: Metric System: 1 m = 10 dm: meters: m: Metric System: base unit: decameters: dam or dkm: Metric System: 1 dam = 10 m: hectometers: hm: Metric System: 1 hm = m: kilometers: km: Metric System: 1 km = 1, m: megameters: Mm: Metric System: 1 Mm = .
The SI unit symbol is m. The metre was originally defined in as one ten-millionth of the distance from the equator to the North Pole along a great circle , so the Earth's circumference is approximately 40 km. In , the metre was redefined in terms of a prototype metre bar the actual bar used was changed in In , the metre was redefined in terms of a certain number of wavelengths of a certain emission line of krypton The current definition was adopted in and modified slightly in to clarify that the metre is a measure of proper length.
Metre is the standard spelling of the metric unit for length in nearly all English-speaking nations except the United States     and the Philippines,  which use meter. Other Germanic languages , such as German, Dutch, and the Scandinavian languages,  likewise spell the word meter. Measuring devices such as ammeter , speedometer are spelled "-meter" in all variants of English. Ultimately the word came from the sanskrit "mita", meaning "measured". In Jean Picard measured the length of a " seconds pendulum " a pendulum with a period of two seconds at the Paris observatory.
He found the value of He proposed a universal toise French: Toise universelle which was twice the length of the seconds pendulum. They arrived at a figure for the solar parallax of 9.
They were also the first astronomers to have access to an accurate and reliable value for the radius of Earth, which had been measured by their colleague Jean Picard in as thousand toises. Picard's geodetic observations had been confined to the determination of the magnitude of the Earth considered as a sphere, but the discovery made by Jean Richer turned the attention of mathematicians to its deviation from a spherical form.
Since Eratosthenes , the measurement of meridian arcs had been used by geographers to assess the size of the globe. Since the end of the 17th century, geodesy has been concerned with measuring the Earth, in order to determine not only its size, but also its shape.
Indeed, first taken for a sphere, the Earth was then considered as a spheroid of revolution. In the 18th century, geodesy was at the center of the debates between Cartesians and Newtonians in France, because it was the means of empirically demonstrating the theory of gravity. In addition to its importance for mapping, determining the figure of the Earth was then a problem of the utmost importance in astronomy , since the radius of the Earth was the unit to which all celestial distances were to be referred.
As a result of the French Revolution , the French Academy of Sciences charged a commission with determining a single scale for all measures. From to France adopted this definition of the metre as its official unit of length based on results from this expedition combined with those of the Geodesic Mission to Peru. In the 19th century, geodesy underwent a revolution with advances in mathematics as well as progress of observation instruments and methods with the taking into account of the personal equation.
The application of the least squares method to meridian arc measurements demonstrated the importance of the scientific method in geodesy. On the other hand, the invention of the telegraph made it possible to measure parallel arcs, and the improvement of the reversible pendulum gave rise to the study of the Earth's gravitational field. A more accurate determination of the Figure of the Earth would soon result from the measurement of the Struve Geodetic Arc — and would have given another value for the definition of this standard of length.
This did not invalidate the metre but highlighted that progresses in science would allow better measurement of Earth's size and shape. In , Carl Friedrich Gauss studied the Earth's magnetic field and proposed adding the second to the basic units of the metre and the kilogram in the form of the CGS system centimetre , gram , second.
In , he founded the Magnetischer Verein , the first international scientific association, in collaboration with Alexander von Humboldt and Wilhelm Edouard Weber. Geophysics or the study of the Earth by the means of physics preceded physics and contributed to the development of its methods.
It was primarily a natural philosophy whose object was the study of natural phenomena such as the Earth's magnetic field, lightning and gravity. The coordination of the observation of geophysical phenomena in different points of the globe was of paramount importance and was at the origin of the creation of the first international scientific associations. He had carried to America a large collection of scientific books and numerous scientific instruments and standards, among them a standard metre, made at Paris in A long course of special training secured in Switzerland , France and Germany had made him the foremost practical geodesist living in the United States in the beginning of the 19th century.
In , he was appointed first Superintendent of the Survey of the Coast. The creative side of Hassler was seen in the design of new surveying instruments.
Instead of bringing different bars in actual contact during the process of baseline measurements, he used four two-metre iron bars fastened together totaling eight meters in length and optical contact. As early as February—March , Ferdinand Rudolph Hassler, standardized the bars of his device which were actually calibrated on the metre. The latter became the unit of length for geodesy in the United States. In at the second general conference of the International Association of Geodesy held in Berlin, the question of an international standard unit of length was discussed in order to combine the measurements made in different countries to determine the size and shape of the Earth.
In the s and in light of modern precision, a series of international conferences was held to devise new metric standards. This new organisation was to construct and preserve a prototype metre bar, distribute national metric prototypes, and maintain comparisons between them and non-metric measurement standards. The BIPM's thermometry work led to the discovery of special alloys of iron-nickel, in particular invar , for which its director, the Swiss physicist Charles-Edouard Guillaume , was granted the Nobel Prize for physics in If precision metrology had needed the help of geodesy, the latter could not continue to prosper without the help of metrology.
It was then necessary to define a single unit in order to express all the measurements of terrestrial arcs, and all determinations of the force of gravity by the mean of pendulum. Metrology had to create a common unit, adopted and respected by all civilized nations.
Moreover, at that time, statisticians knew that scientific observations are marred by two distinct types of errors, constant errors on the one hand, and fortuitous errors, on the other hand. The effects of the latters can be mitigated by the least squares method. Constant or regular errors on the contrary must be carefully avoided, because they arise from one or more causes which constantly act in the same way, and have the effect of always altering the result of the experiment in the same direction.
They therefore deprive of any value the observations that they impinge. For metrology the matter of expansibility was fundamental; as a matter of fact the temperature measuring error related to the length measurement in proportion to the expansibility of the standard and the constantly renewed efforts of metrologists to protect their measuring instruments against the interfering influence of temperature revealed clearly the importance they attached to the expansion-induced errors.
It was thus crucial to compare at controlled temperatures with great precision and to the same unit all the standards for measuring geodetic baselines, and all the pendulum rods. Only when this series of metrological comparisons would be finished with a probable error of a thousandth of a millimetre would geodesy be able to link the works of the different nations with one another, and then proclaim the result of the measurement of the Globe.
As the figure of the Earth could be inferred from variations of the seconds pendulum length with latitude , the United States Coast Survey instructed Charles Sanders Peirce in the spring of to proceed to Europe for the purpose of making pendulum experiments to chief initial stations for operations of this sort, in order to bring the determinations of the forces of gravity in America into communication with those of other parts of the world; and also for the purpose of making a careful study of the methods of pursuing these researches in the different countries of Europe.
Nowadays the practical realisation of the metre is possible everywhere thanks to the atomic clocks embedded in GPS satellites. In , James Clerk Maxwell suggested that light emitted by an element be used as the standard both for the metre and for the second.
These two quantities could then be used to define the unit of mass. In , the standard metre was first measured with an interferometer by Albert A.
Michelson , the inventor of the device and an advocate of using some particular wavelength of light as a standard of length. By , interferometry was in regular use at the BIPM.
To further reduce uncertainty, the 17th CGPM in replaced the definition of the metre with its current definition, thus fixing the length of the metre in terms of the second and the speed of light : . To further facilitate reproducibility from lab to lab, the 17th CGPM also made the iodine-stabilised helium—neon laser "a recommended radiation" for realising the metre.
Practical realisation of the metre is subject to uncertainties in characterising the medium, to various uncertainties of interferometry, and to uncertainties in measuring the frequency of the source. Errors in the theoretical formulas used are secondary.
Air is only one possible medium to use in a realisation of the metre, and any partial vacuum can be used, or some inert atmosphere like helium gas, provided the appropriate corrections for refractive index are implemented.
The metre is defined as the path length travelled by light in a given time, and practical laboratory length measurements in metres are determined by counting the number of wavelengths of laser light of one of the standard types that fit into the length,  and converting the selected unit of wavelength to metres. Three major factors limit the accuracy attainable with laser interferometers for a length measurement:  .
Of these, the last is peculiar to the interferometer itself. The conversion of a length in wavelengths to a length in metres is based upon the relation. Here n is the refractive index of the medium in which the measurement is made, and f is the measured frequency of the source. Although conversion from wavelengths to metres introduces an additional error in the overall length due to measurement error in determining the refractive index and the frequency, the measurement of frequency is one of the most accurate measurements available.
After the July Revolution of the metre became the definitive French standard from At that time it had already been adopted by Ferdinand Rudolph Hassler for the U. S Survey of the Coast. It is the property of the American Philosophical Society, to whom it was presented by Mr.
Hassler, who had received it from Tralles , a member of the French Committee charged with the construction of the standard metre by comparison with the toise, which had served as unit of length in the measurement of the meridional arcs in France and Peru. It possesses all the authenticity of any original metre extant, bearing not only the stamp of the Committee but also the original mark by which it was distinguished from the other bars during the operation of standardising.
According to the decision of the Congress of the United States , the British Parliamentary Standard from was introduced as the unit of length. SI prefixes can be used to denote decimal multiples and submultiples of the metre, as shown in the table below. Long distances are usually expressed in km, astronomical units Within this table, "inch" and "yard" mean "international inch" and "international yard"  respectively, though approximate conversions in the left column hold for both international and survey units.
A simple mnemonic aid exists to assist with conversion, as three "3"s:. The ancient Egyptian cubit was about 0. From Wikipedia, the free encyclopedia. SI unit of length. This article is about the unit of length.
For other uses of "metre" or "meter", see Meter disambiguation. Main article: History of the metre. Main article: Metrication. National Institute of Standards and Technology. Retrieved 28 September A Sankrit English Dictionary. Delhi: Motilal Banarsidass. ISBN Thus the spellings "meter,"…rather than "metre," However, in the U. English translation published by the U. Thus, the spelling metre is referred to as the "international spelling"; the spelling meter , as the "American spelling".