Knot (unit of measurement)

Aircraft speed indicator, graduated in knots.

The prevalence of the knot as a unit of measurement is associated with the significant convenience of its use in navigation calculations: a ship moving at a speed of 1 knot along the meridian passes one arc minute of geographic latitude in one hour.

The origin of the name is related to the principle of using a sector log. The speed of the vessel was determined as the number of knots on the line (thin cable) that passed through the hand of the measurer in a certain time (usually 15 seconds or 1 minute). In this case, the distance between adjacent nodes on the line and the measurement time were selected in such a way that this amount was numerically equal to the speed of the vessel, expressed in nautical miles per hour.

A knot is an independent unit of speed. To say: “The ship is sailing at a speed of 36 knots per hour” is incorrect. The absurdity of such an expression is very well described in the story “The Flying Dutchman”, an excerpt from which is given below.
“Tell me, captain, what is our speed? - Raising his glasses from his notebook, the guest asked again.
Guzhevoy already opened his mouth to answer with his usual wit, that there were six knots per hour - in the first, and in the second they didn’t pull even three, but Piychik warned him:
“As much as it should be: full speed, twelve knots.”
The lag cable, released while moving from the stern, broke into knots at a distance of 1/120 of a mile (50 feet). By counting the number of knots that travel in half a minute (1/120 of an hour), you can find out the speed in nautical miles per hour. It follows that the expression “30 knots per hour” is clearly meaningless: it turns out that the ship, instead of a decent speed of 56 km/h, drags 1500 feet (470 m) per hour, which is both incorrect and offensive.

The hub and international nautical mile are widely used in maritime and air transport. Knots were considered the most common measurement in England until 1965, but later they became known as miles.

Notes

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See what “Knot (unit of measurement)” is in other dictionaries:

KNOT- KNOT, 1). In anatomy, thickening or enlargement of an organ or tissue, such as a lymph node or sinoatrial node, of nervous tissue that controls the rhythm of the heart. 2). In botany, a node is a place on a plant stem from which a leaf or leaves arise. 3) ... Scientific and technical encyclopedic dictionary

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Node (in navigation)

Knot (speed)- Knot is a unit of speed equal to one nautical mile per hour. Since there are different definitions of a nautical mile, a knot can have different meanings. By international definition, one knot is equal to 1.852 km/h (exactly) or... ... Wikipedia

Knot (measure)- Knot is a unit of speed equal to one nautical mile per hour. Since there are different definitions of a nautical mile, a knot can have different meanings. By international definition, one knot is equal to 1.852 km/h (exactly) or... ... Wikipedia

node- noun, m., used. compare often Morphology: (no) what? node, what? knot, (I see) what? node, what? knot, about what? about the node; pl. What? nodes, (no) what? nodes, what? nodes, (I see) what? nodes, what? knots, about what? about knots 1. A knot is called a tightened... ... Dmitriev's Explanatory Dictionary

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Nautical mile- The nautical mile is a unit of distance used in navigation and aviation. The nautical mile was originally defined as the length of a great circle on the surface of the globe measuring one minute of arc. Thus, moving to... Wikipedia

kinematic units- ▲ unit of measurement is speed knot. gal is a unit of acceleration. hertz unit of frequency... Ideographic Dictionary of the Russian Language

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1 kilometer per hour [km/h] = 0.539956803455724 knot [kt]

Initial value

Converted value

meter per second meter per hour meter per minute kilometer per hour kilometer per minute kilometer per second centimeter per hour centimeter per minute centimeter per second millimeter per hour millimeter per minute millimeter per second foot per hour foot per minute foot per second yard per hour yard per minute yard per second mile per hour mile per minute miles per second knot knot (UK) speed of light in vacuum first cosmic speed second cosmic speed third cosmic speed speed of rotation of the Earth speed of sound in fresh water speed of sound in sea water (20°C, depth 10 meters) Mach number (20°C, 1 atm) Mach number (SI standard)

Heat transfer coefficient

More about speed

General information

Speed is a measure of the distance traveled in a certain time. Speed can be a scalar quantity or a vector quantity - the direction of movement is taken into account. The speed of movement in a straight line is called linear, and in a circle - angular.

Speed measurement

Average speed v found by dividing the total distance traveled ∆ x for total time ∆ t: v = ∆x/∆t.

In the SI system, speed is measured in meters per second. Kilometers per hour in the metric system and miles per hour in the US and UK are also widely used. When, in addition to the magnitude, the direction is also indicated, for example, 10 meters per second to the north, then we are talking about vector velocity.

The speed of bodies moving with acceleration can be found using the formulas:

a, with initial speed u during the period ∆ t, has a finite speed v = u + a×∆ t.
A body moving with constant acceleration a, with initial speed u and final speed v, has an average speed ∆ v = (u + v)/2.

Average speeds

Speed of light and sound

According to the theory of relativity, the speed of light in a vacuum is the highest speed at which energy and information can travel. It is denoted by the constant c and is equal to c= 299,792,458 meters per second. Matter cannot move at the speed of light because it would require an infinite amount of energy, which is impossible.

The speed of sound is usually measured in an elastic medium, and is equal to 343.2 meters per second in dry air at a temperature of 20 °C. The speed of sound is lowest in gases and highest in solids. It depends on the density, elasticity, and shear modulus of the substance (which shows the degree of deformation of the substance under shear load). Mach number M is the ratio of the speed of a body in a liquid or gas medium to the speed of sound in this medium. It can be calculated using the formula:

M = v/a,

Where a is the speed of sound in the medium, and v- body speed. Mach number is commonly used in determining speeds close to the speed of sound, such as airplane speeds. This value is not constant; it depends on the state of the medium, which, in turn, depends on pressure and temperature. Supersonic speed is a speed exceeding Mach 1.

Vehicle speed

Below are some vehicle speeds.

Passenger aircraft with turbofan engines: The cruising speed of passenger aircraft is from 244 to 257 meters per second, which corresponds to 878–926 kilometers per hour or M = 0.83–0.87.
High-speed trains (like the Shinkansen in Japan): such trains reach maximum speeds of 36 to 122 meters per second, that is, from 130 to 440 kilometers per hour.

Animal speed

The maximum speeds of some animals are approximately equal to:

Human speed

People walk at speeds of about 1.4 meters per second, or 5 kilometers per hour, and run at speeds of up to about 8.3 meters per second, or 30 kilometers per hour.

Examples of different speeds

Four-dimensional speed

In classical mechanics, vector velocity is measured in three-dimensional space. According to the special theory of relativity, space is four-dimensional, and the measurement of speed also takes into account the fourth dimension - space-time. This speed is called four-dimensional speed. Its direction may change, but its magnitude is constant and equal to c, that is, the speed of light. Four-dimensional speed is defined as

U = ∂x/∂τ,

Where x represents a world line - a curve in space-time along which a body moves, and τ is the "proper time" equal to the interval along the world line.

Group speed

Group velocity is the speed of wave propagation, describing the speed of propagation of a group of waves and determining the speed of wave energy transfer. It can be calculated as ∂ ω /∂k, Where k is the wave number, and ω - angular frequency. K measured in radians/meter, and the scalar frequency of wave oscillation ω - in radians per second.

Hypersonic speed

Hypersonic speed is a speed exceeding 3000 meters per second, that is, many times faster than the speed of sound. Solid bodies moving at such speeds acquire the properties of liquids, since, thanks to inertia, the loads in this state are stronger than the forces that hold the molecules of a substance together during collisions with other bodies. At ultrahigh hypersonic speeds, two colliding solids turn into gas. In space, bodies move at exactly this speed, and engineers designing spacecraft, orbital stations and spacesuits must consider the possibility of a station or astronaut colliding with space debris and other objects when working in outer space. In such a collision, the skin of the spacecraft and the spacesuit suffer. Hardware developers conduct hypersonic collision experiments in special laboratories to determine how intense impacts the suits can withstand, as well as the skin and other parts of the spacecraft, such as fuel tanks and solar panels, testing their strength. To do this, spacesuits and skin are exposed to impacts from various objects from a special installation at supersonic speeds exceeding 7500 meters per second.

Zel is a unit of speed equal to one nautical mile per hour.

The hub and international nautical mile are widely used in maritime and air transport. Knots were considered the most common measurement in England until 1965, but after the re-decision they began to be called...

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What is a sea knot? The speed at which a ship floats on the waves is determined by sailors in knots. So what is this unit of speed and why is it called a “knot”?

The fact is that ancient sailors used a special device, which they called a “log,” to measure the speed of their ship. The log at that time was a simple log with a rope tied to it. Knots were tied along the entire length of this rope, at the same distance from each other. The other end of the rope was secured to the side of the ship.

To measure the speed at which a ship was sailing, an ancient sailor threw a log overboard and counted how many knots of unwinding rope would pass through his hands in a certain period of time and, by their number, determined the speed of the ship. And to designate it, sailors in the old days began to use the word “knot,” which is still used today.

What does a modern maritime “knot” mean? The speed at which...

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Instructions

In maritime practice, it is customary to measure the speed of a ship in knots. One knot is the speed that allows you to travel one nautical mile in an hour. In terms of our usual kilometers, one knot is 1.852 kilometers per hour. Accordingly, to convert knots to kilometers per hour, it is enough to multiply the speed in knots by 1.852.

If you have the Internet at hand, to convert knots to kilometers, just go to the Google search engine and enter a phrase like “5 knots to kilometers.” Google is a smart search engine and has a built-in calculator for converting units, so it will show the information you are looking for on the results page. For example, for the example search phrase it will show “5 knots = 9.26 kilometers”. Kilometers here mean speed in kilometers per hour.

The existence of knots in maritime practice is closely related to the concept of “nautical mile”. Initially, it was taken as the length of the Earth's surface measuring one...

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When the first ships began to sail the sea, navigators could not determine their location on the open sea with great accuracy. Then they learned to determine the longitude and latitude of the place where the ship was located. Latitude is the distance north and south of the equator. Longitude is the distance west or east of zero degree. It was agreed that zero degrees of longitude would be the longitude at which the observatory in Greenwich, England, is located.

To determine longitude, ancient sailors calculated how far they sailed in a certain period of time. To do this, they used a special device - a “lag”. It was an ordinary log to which a rope was tied. The log was thrown overboard from the stern of the ship, and they waited until the rope became taut.

Knots were tied at regular intervals along the entire length of the rope. The sailor, lowering the rope, counted how many knots passed through his hands in a certain time. This is how the speed of the ship was calculated. Sailors began to use...

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Home > Other > Why is speed measured in knots at sea?

Why is speed measured in knots at sea? Form for quickly converting speed in knots to km/h.
Speed in knots:
Fractions through a dot
Result:
A little history about sea knots.

Measuring speed in knots has happened historically. In those ancient times, it was quite difficult for sailors to navigate the sea. Gradually they learned to determine longitude and latitude by the distances from the equator or zero degree. When they tried to determine what degree was zero, it was at the observatory in the city of Greenwich, and they decided that zero degree would pass through this place.

But in those years there were no navigation instruments, and in order to determine the distance it was necessary to somehow measure the distance traveled. A special device was invented - a “lag”. This is the most ordinary log with a rope tied to it, which they threw overboard and waited for the rope to stretch.

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§ 9. Marine measures of length and speed The unit of measurement of distances at sea is the nautical mile, equal to the linear length of 1" arc of the meridian of the globe, i.e. 1852 m 66070 ft. In addition to the nautical mile, the following units of length are also accepted for measuring distance at sea :
When solving questions of increased accuracy, it should be remembered that the Earth is not a sphere, but a spheroid. Thus, the length of one nautical mile, adopted in the USSR, corresponds to the linear length of 1" of the earth's spheroid at a latitude of 44°. The length of 1" arc of such a spheroid in the equator region is 1842.9 m, at the pole - 1861.6 m. The difference is 18.7 m (about 1%) is neglected in practice.

The speed of a sea vessel is measured in knots, i.e. the number of nautical miles it travels in 1 hour. They say, for example, that a ship has a speed of 12 knots, i.e. it travels 12 nautical miles per hour.

When navigating on inland waterways, metric units are often used to measure distance and speed....

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Since there are different definitions of a nautical mile, a knot can have different meanings.

By international definition, one knot is equal to 1.852 km/h (exact) or 0.5144444 m/s. This unit of measurement, although non-systemic, is allowed for use along with SI units.

The origin of the name is related to the principle of using sector lag. The speed of the vessel was determined as the number of knots on the line (thin cable) that passed through the hand of the measurer in a certain time (usually 15 seconds).

The hub and international nautical mile are widely used in maritime and air transport. Knots were considered the most common measurement in England until 1965, but after a re-decision they became known as miles.

Green is a unit of speed equal to one nautical mile per hour.

Since there are different definitions of a nautical mile, accordingly, the node may have different...

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Sometimes the notation is also used kt) - unit of speed. Equal to the speed of uniform motion at which a body travels a distance of one nautical mile in one hour. It is used in maritime and aviation practice, in meteorology, and is the basic unit of speed in navigation.

According to international definition, one knot is equal to 1852 m/h exactly or 0.51444... m/s. This unit of measurement, although non-systemic, is allowed for use along with units of the International System of Units (SI). In the Russian Federation, the unit is approved for use as an off-system unit without a time limit with the scope of application “marine navigation”. The unit is included in the All-Russian Classifier of Units of Measurement.

The origin of the name is related to the principle of using a manual sector log, which in its simplest form was a plank tied to a long thin cable (lagline) in such a way that when thrown overboard of a moving vessel, it would be braked by the water. Knots were tied on the laglin at equal distances from each other; the distance was selected such that the number of knots on the lagline being etched overboard, escaping from the lag view and passing through the measuring hand in a certain time, was numerically equal to the speed of the vessel, expressed in nautical miles per hour.

A knot is an independent unit of speed. To say: “The ship is moving at a speed of 36 knots per hour” is incorrect. The fallacy of such an expression is illustrated in the story “The Flying Dutchman” by L. S. Sobolev, an excerpt from which is given below:

Tell me, captain, what is our speed? - Raising his glasses from his notebook, the guest asked again.
Guzhevoy already opened his mouth to answer with his usual wit, that there were six knots per hour - in the first, and in the second they didn’t pull even three, but Piychik warned him:
Allowed: full speed, twelve knots.

- Leonid Sergeevich Sobolev. Stories of Captain 2nd Rank V. L. Kirdyaga, heard from him during the “Great Seat”

Knot and nautical mile are widely used in maritime and air transport. The knot is the only widely used unit of speed that has its own name. Decimal prefixes (kilo-, milli-, etc.), which are used to form multiples and submultiples, are not used with the “knot” unit.

Knots and miles per hour should not be confused. A knot is one nautical (or nautical) mile (1852 meters) per hour, and "mile per hour" (English mph, miles per hour), widely used in Great Britain and North America, is a statute mile (1609 meters) in hour.

Before the introduction of the international knot, similar knot definitions were also used, based on different definitions of the nautical mile. In the USA, until 1952, a knot based on the American nautical mile (1852.249 m) was used. In Great Britain until 1970 (as well as in the countries of the British Commonwealth), a unit based on the British or Admiralty nautical mile (1852.184 m) was used. The difference between both definitions and the modern definition of a node is about 0.01% and is insignificant in almost all practical cases.

There is a simple mnemonic for quickly mentally converting knots to kilometers per hour: “multiply by two and subtract 10 percent.” For example, speed 15 knots, 15×2 = 30 km/h, subtract 10% = 3 km/h, we get 27 km/h. The rule gives values with an error of less than 3%. To recalculate km/h → nodes, the reverse algorithm is used: the speed in km/h is divided by 2 and 10% is added to the resulting value. For example, 20 km/h → 10 knots → 11 knots(the exact value is 10.799136... nodes).

Notes

Regulations on units of quantities allowed for use in the Russian Federation. Approved by Decree of the Government of the Russian Federation No. 879 of October 31, 2009.
The international designation “kn” (from the English “knot”) is established by the ISO 80000-3 standard.
Not recommended as it is the same as the international designation for kiloton.
Dengub V. M., Smirnov V. G. Units of quantities. Dictionary-reference book. - M.: Standards Publishing House, 1990. - P. 117. - 240 p. - ISBN 5-7050-0118-5.

And speed. Units of measurement can be difficult to understand for non-marine people, so determining distances and speeds of ships can present some difficulties. The main unit of speed used at sea is the knot. What it is equal to and how to calculate speed using it will be discussed in the article.

Nautical mile

At sea, the main measure of distance is the mile. It is important to note that a sea mile and a land mile are different things. The land length is 1609 meters. A nautical mile is equal to the length of one minute of the earth's meridian line. The Earth's meridian is conventionally an arc, and its length is measured in degrees, minutes and seconds. Thus, the length of one nautical mile is 1852 meters. The difference between a land mile and a nautical mile is significant, so it is important not to confuse these units of measurement.

In addition to the mile, distance at sea is measured using units such as feet, inches, yards, fathoms and sea cables.

Sea knot: ship speed

Having dealt with distance at sea, we need to turn to the concept of speed. To determine speed at sea, the concept is used - the unit of speed with which a ship will travel one nautical mile in an hour. How many km are there in a maritime hub? It turns out that one sea knot is 1.852 km per hour. Thus, 10 sea knots is 18.5 km per hour, 100 sea knots is 185 km per hour, and so on.

Example of calculating ship speed

The ship is moving at a speed of 20 nautical knots. He needs to cover a distance of 100 km to his destination. What is his speed in kilometers, and how long will it take him to cover this distance?

First you need to convert the speed from knots to kilometers; to do this, 20 needs to be multiplied by 1.852. It turns out that the speed of the ship in kilometers is 37 km per hour.

Then divide the distance of 100 km by the ship's speed of 37 km/h. It turns out that the ship will take approximately 2.7 hours to reach its destination, traveling at a speed of 20 nautical knots.

Vessel speeds depend on their size, technical characteristics, purpose and other factors. and passenger liners usually travel at a speed of 10-20 knots, and military ships are capable of much higher rates of movement. For example, the HCMS Bras D"Or 400 warship has a speed of 62 knots (116 km per hour).

Origin of the term "maritime knot"

Shipping is one of the oldest human activities. It is obvious that in ancient times there were no compasses, locators, navigators and other technical achievements of later times. However, sailors needed to look for some landmarks in order to determine their location. They navigated by the stars, the moon, lighthouses, the outlines of coastal relief, and so on.

A special invention was used to determine the distance traveled. It was called a log and was a log with a rope tied to it. Knots were tied on the rope at equal distances from each other. The log was thrown from the stern of the ship. When the rope was stretched, the sailor counted the number of knots passed through his hands during the movement of the ship.

This is how the tradition of measuring speed with sea knots was established, although the modern knot has a different size than in ancient times. In modern navigation, the log is still used to measure the speed of the ship. It looks, of course, different than in the past, and is a special device.

So, at sea, the calculation of speed in sea knots has been carried out since ancient times. A knot corresponds to the speed at which a ship will travel one nautical mile in an hour. To convert speed in knots to speed in kilometers, multiply the knots by 1.852 (the length of one nautical mile).