s; and. 1. The stretch of something; distance between whom, than l. Measures of length. Measure length and width. D. straight line segment. D. way. D. shipping channel. Full length. Three meters long. 2. Duration, duration (about time). D. working day. ... ... encyclopedic Dictionary
LENGTH, lengths, pl. no, female The extension of a line, plane, body in the direction in which the two extreme points (lines, planes, bodies) lie at the greatest distance from one another. Items are measured in length, width and height. Table length. Measures… … Dictionary Ushakov
Female stretch along, valley; psk. valley, valley, tver., psk. length, perm. share; for the length of space, body or thing is usually taken the direction of its greatest extent; length, width and height, or a level measure along and across and a measure along ... Dahl's Explanatory Dictionary
Exist., f., use. comp. often Morphology: (no) what? length for what? length, (see) what? length than? length about what? about length; pl. What? length, (no) what? length for what? lengths, (see) what? length than? lengths, what? about lengths 1. The length of an object is ... Dictionary of Dmitriev
1) The length of a straight line segment is the distance between its ends. 2) The length of the broken line is the sum of the lengths of its links. 3) The length of the arc of the curve is the limit of the length of the broken line inscribed in it, when the number of its links increases indefinitely, and the length of each link tends to zero ... Big Encyclopedic Dictionary
Duration, length, distance, duration, longitude; perimeter, footage, picket, extension, apothem, extension Dictionary of Russian synonyms. length 1. length, length 2. see duration ... Synonym dictionary
length- LENGTH1, s, w The length of an object, the distance between its two extreme points, located on the same line or one plane and located at the greatest (in contrast to width) distance from each other. Pavel increased the length of the trousers in ... ... Explanatory dictionary of Russian nouns
English long A message about the presence of securities in the dealer, made in exchange jargon, where the number of shares is replaced by the term length. Dictionary of business terms. Akademik.ru. 2001 ... Glossary of business terms
From *length, cf. other Russian d (b) for length (e.g., in Khozh. igum. Dan. 18). From to last; cf. Ukrainian duration, st. glory. prolong μηκύνειν, Czech. dlim, dlit. Kindred Praslav. * dьlgъ (see long); cf. Bernecker 1, 252 ff.; Trautman, BSW 55; mi. EW 55.… … Etymological dictionary Russian language by Max Fasmer
LENGTH, s, pl. (special) lengths, lengths, lengths, wives. The size, length of something. in that direction, in which the two extreme points of a line, plane, body lie, in contrast to the width, at the greatest distance from each other. Measure the table in length and in ... ... Explanatory dictionary of Ozhegov
Books
- Length, area, volume, G. A. Merzon, I. V. Yashchenko. The sixth book in the series `School Mathematical Circles` is devoted to various approaches to comparing and calculating areas and volumes and is intended for classes with schoolchildren in grades 6-11. In her…
- The length of the shadow from a rotten stump, Valentin Pikul. “... in ancient times, the banks of the Luga were completely lined with villages, very densely populated by peasants and the nobility, and the river itself was famous for navigation in ancient times, even ...
> Length
Explore length in physics: how the length is indicated, the letter and length formula, how to find. Read about the designation of length, unit of measure, definition, types of quantities.
Length is one of the basic characteristics of measuring an object in physics.
Learning task
- Understand the definition of the length of an object.
Key Points
- Length is the measure of the longest dimension of the body.
- Deformation is a change in length.
- The unit of measurement is meter.
Terms
- Special Relativity: reconciles the principle of relativity with the reference that the speed of light remains constant in all frames of reference.
- Dimension - a measure of spatial extent in a particular direction (height, width, depth, length).
Length
Length in physics reflects one of the characteristics of an object. Moreover, this concept is widely used in everyday sense. For example, you can cut a certain length of wire. It can differ from height (vertical length) or width (distance between sides).
Length is a measure of one dimension, area is two (the square of length), and volume is three. Because of special theory relativity, the length is not considered constant in all frames of reference. Therefore, your meter ruler will not display one value. It changes depending on the observer.
Units
What is the unit of length in physics? One of the oldest measurements is the cubit (from the tip of the finger to the elbow). Then it was divided into a leg, arm or finger. Could also increase - a step. However, such units are not stable, because the size of the cubit varies depending on the person.
In physics, length has become synonymous with distance. Units can be based on body parts or distance traveled between certain points. The official is the meter and is determined in relation to the speed of light. Also used in centimeters and kilometers. In the English system - inch, foot, yard and mile. When it comes to cosmic distances, they use a light year and a parsec.
Metric length 1 km is equivalent to 0.62137 miles
Value is something that can be measured. Concepts such as length, area, volume, mass, time, speed, etc. are called quantities. The value is measurement result, it is determined by a number expressed in certain units. The units in which a quantity is measured are called units of measurement.
To designate a quantity, a number is written, and next to it is the name of the unit in which it was measured. For example, 5 cm, 10 kg, 12 km, 5 min. Each value has an infinite number of values, for example, the length can be equal to: 1 cm, 2 cm, 3 cm, etc.
The same value can be expressed in different units, for example, kilogram, gram and ton are units of weight. The same value in different units is expressed by different numbers. For example, 5 cm = 50 mm (length), 1 hour = 60 minutes (time), 2 kg = 2000 g (weight).
To measure a quantity means to find out how many times it contains another quantity of the same kind, taken as a unit of measurement.
For example, we want to know the exact length of a room. So we need to measure this length using another length that is well known to us, for example, using a meter. To do this, set aside a meter along the length of the room as many times as possible. If he fits exactly 7 times along the length of the room, then its length is 7 meters.
As a result of measuring the quantity, one obtains or named number, for example 12 meters, or several named numbers, for example 5 meters 7 centimeters, the totality of which is called composite named number.
Measures
In each state, the government has established certain units of measurement for various quantities. A precisely calculated unit of measurement, taken as a model, is called standard or exemplary unit. Model units of the meter, kilogram, centimeter, etc., were made, according to which units for everyday use are made. Units that have come into use and approved by the state are called measures.
The measures are called homogeneous if they serve to measure quantities of the same kind. So, grams and kilograms are homogeneous measures, since they serve to measure weight.
Units
The following are units of measurement for various quantities that are often found in math problems:
Measures of weight/mass
- 1 ton = 10 centners
- 1 centner = 100 kilograms
- 1 kilogram = 1000 grams
- 1 gram = 1000 milligrams
- 1 kilometer = 1000 meters
- 1 meter = 10 decimeters
- 1 decimeter = 10 centimeters
- 1 centimeter = 10 millimeters
- 1 sq. kilometer = 100 hectares
- 1 hectare = 10000 sq. meters
- 1 sq. meter = 10000 sq. centimeters
- 1 sq. centimeter = 100 sq. millimeters
- 1 cu. meter = 1000 cubic meters decimeters
- 1 cu. decimeter = 1000 cu. centimeters
- 1 cu. centimeter = 1000 cu. millimeters
Let's consider another value like liter. A liter is used to measure the capacity of vessels. A liter is a volume that is equal to one cubic decimeter (1 liter = 1 cubic decimeter).
Measures of time
- 1 century (century) = 100 years
- 1 year = 12 months
- 1 month = 30 days
- 1 week = 7 days
- 1 day = 24 hours
- 1 hour = 60 minutes
- 1 minute = 60 seconds
- 1 second = 1000 milliseconds
In addition, time units such as quarter and decade are used.
- quarter - 3 months
- decade - 10 days
The month is taken as 30 days, unless it is required to specify the day and name of the month. January, March, May, July, August, October and December - 31 days. February in a simple year has 28 days, February in a leap year has 29 days. April, June, September, November - 30 days.
A year is (approximately) the time it takes for the Earth to complete one revolution around the Sun. It is customary to count every three consecutive years for 365 days, and the fourth following them - for 366 days. A year with 366 days is called leap year, and years containing 365 days - simple. One extra day is added to the fourth year for the following reason. The time of revolution of the Earth around the Sun does not contain exactly 365 days, but 365 days and 6 hours (approximately). Thus, a simple year is shorter than a true year by 6 hours, and 4 simple years are shorter than 4 true years by 24 hours, that is, by one day. Therefore, one day (February 29) is added to every fourth year.
You will learn about other types of quantities as you further study various sciences.
Measure abbreviations
Abbreviated names of measures are usually written without a dot:
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Measures of weight/mass
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Area measures (square measures)
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Measures of time
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measure of vessel capacity
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Measuring instruments
To measure various quantities, special measuring instruments are used. Some of them are very simple and are designed for simple measurements. Such devices include a measuring ruler, tape measure, measuring cylinder, etc. Other measuring devices are more complex. Such devices include stopwatches, thermometers, electronic scales, etc.
Measuring instruments, as a rule, have a measuring scale (or short scale). This means that dash divisions are marked on the device, and the corresponding value of the quantity is written next to each dash division. The distance between two strokes, next to which the value of the value is written, can be further divided into several smaller divisions, these divisions are most often not indicated by numbers.
It is not difficult to determine which value of the value corresponds to each smallest division. So, for example, the figure below shows a measuring ruler:
The numbers 1, 2, 3, 4, etc. indicate the distances between the strokes, which are divided by 10 identical divisions. Therefore, each division (the distance between the nearest strokes) corresponds to 1 mm. This value is called scale division measuring instrument.
Before you start measuring a quantity, you should determine the value of the division of the scale of the instrument used.
In order to determine the division price, you must:
- Find the two nearest strokes of the scale, next to which the magnitude values are written.
- Subtract the smaller value from the larger value and divide the resulting number by the number of divisions in between.
As an example, let's determine the scale division value of the thermometer shown in the figure on the left.
Let's take two strokes, near which the numerical values of the measured quantity (temperature) are plotted.
For example, strokes with symbols 20 °С and 30 °С. The distance between these strokes is divided into 10 divisions. Thus, the price of each division will be equal to:
(30 °C - 20 °C) : 10 = 1 °C
Therefore, the thermometer shows 47 °C.
Measure various quantities in Everyday life each and every one of us has to do. For example, to come to school or work on time, you have to measure the time that will be spent on the road. Meteorologists measure temperature to predict the weather. Atmosphere pressure, wind speed, etc.
Length is to be understood physical quantity, which is a characteristic of the length of lines in numbers. This concept has several definitions that you should be aware of. Units, tools and devices for measuring length are also different. Therefore, in this article we will tell you how and how to measure the length.
What is length
As we have already said, the concept of length should be understood as a physical quantity. In the narrow sense of the word, it means the size in the longitudinal direction. That is, length can be called the distance between two points of an object that are as far as possible from each other. However, it is important to note that this distance should be measured horizontally, and not vertically, as in the case of height measurements.
In physics, the concept of length is equivalent to the term "distance". It should also be noted that in the vast majority of measurement systems, length is the main unit of measure, with which other units are established. In the international system of units, the unit of length is the meter.
Length units
First of all, it is necessary to say about the metric system, which to this day is the most convenient because of its simplicity. It is based on the unit of measurement meter, and the rest are multiple powers of ten from it. For example, a kilometer is 10 meters cubed. This system greatly simplifies the calculations.
In Rus', a person was a measure of length for a long time. This can be judged by the names of the measures, including span, elbow, sazhen and others. A span is a measure corresponding to the distance between the index and thumb in an extended position, an elbow is the length from a clenched fist to the bend of the elbow, and a fathom is from the end of the fingers of one hand to the end of the other.
From various works of literature, we also know such a unit of distance as a verst. It corresponds to today's 1,066.8 meters. IN Ancient Rus' versts were boundary and travel. The first were used to measure land, the second - distances or paths.
In England and America, other units were used. For a long time in Britain, the following units of length existed:
- mile;
- inch.
The yard is not included in international system units and is equal to 0.9144 meters. Mila came from ancient rome, where it was equal to a thousand double steps of a soldier. This unit is still used in a number of countries where the metric system of measures is not used. IN different countries its size is different. In England, it corresponds to 1.6 kilometers. The foot is also not included in the international system and corresponds to 0.3048 meters. An inch, which is used today in the United States and Britain, is equal to 2.54 centimeters.
In addition, there is also a nautical system for measuring length, which is based on the unit of measurement - the nautical mile. It is equal to the length of one minute of the meridian arc earth ellipsoid. Its length is a variable and depends on latitude. The international nautical mile is 1852 meters.
Length measurement tools
The simplest tool for measuring length is a ruler, which is a narrow plate. On it, as a rule, there are divisions corresponding to the unit of measurement. It can be a millimeter, centimeter, inch, etc. In cartography and geometry, this tool is used only for the purpose of drawing straight lines. Other instruments are used to measure distances, and measuring length with a ruler is considered insufficiently accurate.
Another common tool for measuring the length of an object is a tape measure. It is a tape on a reel, which is wound into the body using a special mechanism. It also has divisions in the form of strokes in accordance with the unit of measurement. Most often there are roulettes 3 or 5 meters long. However, there are also instruments that allow you to measure lengths up to 100 meters.
It should also be said about the end block of length, which is often referred to as KMD. It is an exemplary measure of length (0.5-1000 millimeters), which is made in the form of a round cylinder or cuboid. Gauge block is designed to store and transmit a unit of length. It is with its help that the verification and establishment of the size of measuring instruments takes place.
Distance measuring instruments
The so-called rangefinder is a device for determining the distance from the observer to a certain object. Rangefinders are active and passive. The former include laser, sound and light rangefinders, and the latter are devices that use matching an object to a specific sample or optical parallax.
Separately, we should talk about such a device as a radio range finder. It helps to determine the distance using radio waves. This device is used in military affairs, in space and air navigation and in other areas. This device sets the time it takes for a radio wave to travel from it to a specific object and back. Thus, the distance to a given object is directly proportional to the time interval.
According to the measurement method, such devices are divided into pulse radio range finders and phase ones. In the first case, the delay time of the reflected signal is measured, while in the second, the number of wavelengths that fit in the signal path is determined.
It is important to add that very small distances are usually measured using so-called measuring microscopes. And very large ones are installed by means of satellite and radio navigation systems for measuring length.
When solving geometric problems, students are faced with the question: how to correctly identify certain parts of the drawing? For example, the height of the triangle, the width of the rectangle, the dimensions of the pool. We will find similar notation and in physical tasks: the length of the pendulum, the height from which the body begins to fall ... Therefore, you should know some rules.
In contact with
How the various options are labeled
In a unified measurement system, the designation is used with Latin letters:
- length - letter l , if we are talking about one straight line: a pendulum, a lever, a segment, a straight line. But if it's about geometric figure, for example, a rectangle, then A is used;
- height or depth h ;
- width - B.
What is the SI system, students learn only in high school, therefore, usually in the lower grades, special designations for these quantities are not introduced.
How to define depth?
Why is the same letter used for height and depth? If you build a drawing of a parallelepiped, then here you will mark the height of the figure.
And if you make a drawing of a rectangular pool of the same size as the parallelepiped, then the depth is indicated. Thus, we can say that the height and depth in this case will be one value.
Attention! Height and depth are two quantities that denote the same connecting two opposite planes.
The concept of "depth" is also found in geography. It is displayed in color on maps. If we are talking about expanses of water, then the darker the blue color, the greater the depth, and if we are talking about land, then the lowlands are indicated in dark green.
In drawing, this value is denoted by the letter S. It allows you to create a complete perception of the object, sometimes even with one view.
What is long
What is length and how is this indicator indicated? She points point to point distance, that is, the size of the segment. In geometric problems, it is usually denoted as A. In stereometry, it can be denoted by both A and l (for example, in problems where there is a line that intersects a plane).
In physics, the length of the pendulum, lever arm, etc. in "Dano" is denoted by the letter l , since we are talking about a separate straight line.
The difference between length and height
Length is a value that characterizes the length of the line.
And the height is perpendicular to the opposite plane.
That is, we can conclude that the length differs from the height in that it is part of the figure, coinciding with its face, and the height is obtained as a result of additional construction in the drawing.
The height is carried out in order to obtain new data for solving problems, as well as new figures as part of the original one.
This is the width
The width of an object is necessary in order to understand the shape of both a two-dimensional and a three-dimensional object. As a rule, it is denoted by the letter B.
The width is measured in meters (according to SI). But if the object is too small, then for convenience, smaller units are used:
- decimeters,
- centimeters,
- millimeters,
- micrometers, etc.
And if the subject too big, then the following prefixes are written:
- Kilo- (10³),
- Mega- (10 6),
- Giga- (10 9),
- Tera- (10 12), etc.
Of course, such large units of measurement are necessary, for example, for astronomy. They are also used in quantum physics, microbiology and so on.
What are the sides of a rectangle called?
Unlike a square, the sides of a rectangle pairwise equal and.
This means that the sides forming are different.
Generally, the longer side of a rectangle is called its length, and the width of a rectangle is its short side.
Important! Knowing data such as the length and width of a rectangle, you can find its perimeter, area, length of the diagonals and the angle between them. It is always possible to describe around a rectangle. These properties also work in reverse.
What are the dimensions of length, width and height according to SI
According to a single measurement system, length, height and width are measured in meters. But sometimes, if it is a fractional or multi-digit number, multiple units of measurement are used in calculations for convenience.
In order to know how to correctly convert units of measurement to larger or vice versa small ones, you need to know prefix values.
- Deca - 10 1,
- Hecto - 10 2,
- Kilo - 10 3,
- Mega - 10 6,
- Giga - 10 9,
- Deci - 10 -1,
- Santi - 10 -2,
- Milli - 10 -3,
- Micro - 10 -6,
- Nano - 10 -9.
After calculations, these units must be converted to meters.
There are also off-system units, but they are very rare:
- mile - 1.6 km;
- foot - 12 inches - 0.3048 m;
- yard - 36 inches - 91.44 mm;
- inch - 25.4 mm, etc.
When solving problems, such units must be converted to meters.
By doing geometric tasks units of measurement are not given special attention, the main thing is that they were comparable
(if you make calculations in centimeters, then all values \u200b\u200bmust be converted to centimeters).
And when solving physical problems, the answer must be given in meters in accordance with a unified measurement system.
Designations of length, width, height in geometry
We measure geometric parameters
Conclusion
Now you know what letter indicates the length, what the width of the rectangle is measured in, and you can explain to anyone how the various parameters are indicated.