query: what is the si unit of time period

pos: Frequency German physicist Heinrich Hertz. One hertz means that an event repeats once per second. If a TV has a refresh rate of 1 hertz the TV's screen will change (or refresh) its picture once a second. A previous name for this unit was cycles per second (cps). The SI unit for period is the second. A traditional unit of measure used with rotating mechanical devices is revolutions per minute, abbreviated r/min or rpm. 60 rpm equals one hertz. As a matter of convenience, longer and slower waves, such as ocean surface waves, tend to be described by wave period rather

pos: Day daytime may extend beyond one 24 hour period and could even extend to months Day A day, a unit of time, is approximately the period of time during which the Earth completes one rotation with respect to the Sun ("solar day"). In 1960, the second was redefined in terms of the orbital motion of the Earth in year 1900, and was designated the SI base unit of time. The unit of measurement "day", was redefined as 86 400 SI seconds and symbolized "d". In 1967, the second and so the day were redefined by atomic electron transition. A civil day

pos: Day Day A day, a unit of time, is approximately the period of time during which the Earth completes one rotation with respect to the Sun ("solar day"). In 1960, the second was redefined in terms of the orbital motion of the Earth in year 1900, and was designated the SI base unit of time. The unit of measurement "day", was redefined as 86 400 SI seconds and symbolized "d". In 1967, the second and so the day were redefined by atomic electron transition. A civil day is usually 86 400 seconds, plus or minus a possible leap second in Coordinated

pos: Lumen second the SI unit of magnetic flux density. An older name for the lumen second was the lumberg. The photometric unit lumerg, also proposed by the Committee on Colorimetry in 1937, correlates with the old CGS unit erg in the same way that the lumen second correlates with the radiometric unit joule, so that 10 lumerg = 1 lm⋅s. Lumen second In photometry, the lumen second (lm s or lm⋅s) is the SI derived unit of luminous energy. It is based on the lumen, the SI unit of luminous flux, and the second, the SI base unit of time. The lumen

pos: Lumen second Lumen second In photometry, the lumen second (lm s or lm⋅s) is the SI derived unit of luminous energy. It is based on the lumen, the SI unit of luminous flux, and the second, the SI base unit of time. The lumen second is sometimes called the talbot (symbol T). This name was coined in 1937 by the Committee on Colorimetry, Optical Society of America, in honor of the early photographer William Fox Talbot. The talbot is exactly equal to the lumen second: The use of the symbol T for talbots conflicts with T as the symbol for the tesla,

pos: SI base unit SI base unit The International System of Units (SI) defines seven units of measure as a basic set from which all other SI units can be derived. The SI base units and their physical quantities are the meter for measurement of length, the kilogram for mass, the second for time, the ampere for electric current, the kelvin for temperature, the candela for luminous intensity, and the mole for amount of substance. The SI base units form a set of mutually independent dimensions as required by dimensional analysis commonly employed in science and technology. The names and symbols of SI base

pos: Metre per second squared Metre per second squared The metre per second squared is the unit of acceleration in the International System of Units (SI). As a derived unit, it is composed from the SI base units of length, the metre, and time, the second. Its symbol is written in several forms as m/s, m·s or m s, or less commonly, as m/s/s. As acceleration, the unit is interpreted physically as change in velocity or speed per time interval, i.e. metre per second per second and is treated as a vector quantity. An object experiences a constant acceleration of one metre per second squared

pos: Joule-second Joule-second The joule-second (J s, or J∙s) is the mathematical product of an SI Derived Unit, the joule (J), and an SI Base Unit, the second (s). The joule-second describes the amount of action occurring in a physical system through a summation of energy (or heat, or work) over time. In mathematical terms, this summation of energy means that the quantity of energy becomes integrated over time to give a number - an answer to the question. In SI base units the joule-second becomes kilogram-meters squared-per second or kg∙m∙ s. Dimensional Analysis of the joule-second yields M L T. Note

pos: Time in physics characterize the passage of time with instrumentation, using operational definitions. Simultaneously, our conception of time has evolved, as shown below. In the International System of Units (SI), the unit of time is the second (symbol: formula_1). It is a SI base unit, and it has been defined since 1967 as "the duration of periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom". This definition is based on the operation of a caesium atomic clock. These clocks became practical for use as primary reference standards after about 1955

pos: SI base unit referenced to the values of the fundamental constants, namely the Planck constant ("h"), the electron charge ("e"), the Boltzmann constant ("k"), and the Avogadro constant ("N"). This approach was approved in 2018, only after measurements of these constants were achieved with sufficient accuracy. SI base unit The International System of Units (SI) defines seven units of measure as a basic set from which all other SI units can be derived. The SI base units and their physical quantities are the meter for measurement of length, the kilogram for mass, the second for time, the ampere for electric current, the kelvin

pos: Gal (unit) the gal is deprecated by ISO 80000-3:2006. The gal is a derived unit, defined in terms of the centimeter–gram–second (CGS) base unit of length, the centimeter, and the second, which is the base unit of time in both the CGS and the modern SI system. In SI base units, 1 Gal is equal to 0.01 m/s. The acceleration due to Earth’s gravity (see "standard gravity") at its surface is 976 to 983 Gal, the variation being due mainly to differences in latitude and elevation. Mountains and masses of lesser density within the Earth's crust typically cause variations in gravitational acceleration

pos: Frequency German physicist Heinrich Hertz. One hertz means that an event repeats once per second. If a TV has a refresh rate of 1 hertz the TV's screen will change (or refresh) its picture once a second. A previous name for this unit was cycles per second (cps). The SI unit for period is the second. A traditional unit of measure used with rotating mechanical devices is revolutions per minute, abbreviated r/min or rpm. 60 rpm equals one hertz. As a matter of convenience, longer and slower waves, such as ocean surface waves, tend to be described by wave period rather

pos: Time introduced the CGS (centimetre/gramme/second system) combining fundamental units of length, mass and time. The second is "elastic", because tidal friction is slowing the earth's rotation rate. For use in calculating ephemerides of celestial motion, therefore, in 1952 astronomers introduced the "ephemeris second", currently defined as The CGS system has been superseded by the "Système international". The SI base unit for time is the SI second. The International System of Quantities, which incorporates the SI, also defines larger units of time equal to fixed integer multiples of one second (1 s), such as the minute, hour and day. These are not

pos: Second clocks now set the length of a second and the time standard for the world. SI prefixes are commonly used to measure time less than a second, but rarely for multiples of a second (which is known as metric time). Instead, the non-SI units minutes, hours, days, Julian years, Julian centuries, and Julian millennia are used. Second The second is the SI base unit of time, commonly understood and historically defined as of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds each. Mechanical

pos: Minute arc). Although not an SI unit for either time or angle, the minute is accepted for use with SI units for both. The SI symbols for "minute" or "minutes" are min for time measurement, and the prime symbol after a number, e.g. 5′, for angle measurement. The prime is also sometimes used informally to denote minutes of time. One of the earliest known uses of the minute (and the second) is found in John of Sacrobosco's "Computus" (ca. 1235), where he used them when discussing the length of the tropical year. No earlier records for the origin of the minute

pos: Unit of time Unit of time A unit of time or time unit is any particular time interval, used as a standard way of measuring or expressing duration. The base unit of time in the International System of Units (SI), and by extension most of the Western world, is the second, defined as about 9 billion oscillations of the caesium atom. The exact modern definition, from the National Institute of Standards and Technology is: Historically units of time were defined by the movements of astronomical objects. These units do not have a consistent relationship with each other and require intercalation. For example, the

pos: Unit of time Most of the other units used are multiples or divisions of these three. The graphic also shows the three heavenly bodies whose orbital parameters relate to the units of time. Unit of time A unit of time or time unit is any particular time interval, used as a standard way of measuring or expressing duration. The base unit of time in the International System of Units (SI), and by extension most of the Western world, is the second, defined as about 9 billion oscillations of the caesium atom. The exact modern definition, from the National Institute of Standards and Technology

pos: Planck time Planck time In quantum mechanics, the Planck time () is the unit of time in the system of natural units known as Planck units. A Planck unit is the time required for light to travel in a vacuum a distance of 1 Planck length, which is approximately 5.39 × 10 s. The unit is named after Max Planck, who was the first to propose it. The Planck time is defined as: where: Using the known values of the constants, the approximate equivalent value in terms of the SI unit, the second, is where the two digits between parentheses denote the

pos: Solar time extra-galactic radio sources and then converted to mean solar time by an adopted ratio. The difference between this calculated mean solar time and Coordinated Universal Time (UTC) determines whether a leap second is needed. (The UTC time scale now runs on SI seconds, and the SI second, when adopted, was already a little shorter than the current value of the second of mean solar time.) Solar time Solar time is a calculation of the passage of time based on the position of the Sun in the sky. The fundamental unit of solar time is the day. Two types of solar

neg: Roentgen equivalent man brief period of time, without infringing on the annual total exposure limits. There is no exact conversion from hours to years because of leap years, but approximate conversions are: The ICRP once adopted fixed conversion for occupational exposure, although these have not appeared in recent documents: Therefore, for occupation exposures of that time period, The US National Institute of Standards and Technology (NIST) strongly discourages Americans from expressing doses in rem, in favor of recommending the SI unit. The NIST recommends defining the rem in relation to the SI in every document where this unit is used. For US industries

neg: Centimetre–gram–second system of units base units are therefore the same in both systems, and there is an unambiguous one-to-one correspondence of derived units: Thus, for example, the CGS unit of pressure, barye, is related to the CGS base units of length, mass, and time in the same way as the SI unit of pressure, pascal, is related to the SI base units of length, mass, and time: Expressing a CGS derived unit in terms of the SI base units, or vice versa, requires combining the scale factors that relate the two systems: The conversion factors relating electromagnetic units in the CGS and SI systems

neg: Kilowatt hour watt is equal to 1 J/s. One kilowatt hour is 3.6 megajoules, which is the amount of energy converted if work is done at an average rate of one thousand watts for one hour. The derived unit of energy within the International System of Units (SI) is the joule. The hour is a unit of time "outside the SI", making the kilowatt hour a non-SI unit of energy. The kilowatt hour is not listed among the non-SI units accepted by the BIPM for use with the SI, although the hour, from which the kilowatt hour is derived, is. An electric

neg: Kilowatt hour Kilowatt hour The kilowatt hour (symbol kWh, kW⋅h or kW h) is a unit of energy equal to 3.6 megajoules. If energy is transmitted or used at a constant rate (power) over a period of time, the total energy in kilowatt hours is equal to the power in kilowatts multiplied by the time in hours. The kilowatt hour is commonly used as a billing unit for energy delivered to consumers by electric utilities. The kilowatt hour (symbolized kW⋅h as per SI) is a composite unit of energy equivalent to one kilowatt (1 kW) of power sustained for one hour. One

neg: Slew rate to check the datasheet for the device's slew rate before using it for high-frequency applications. In electronic musical instruments, slew circuitry or software-generated slew functions are used deliberately to provide a portamento (also called "glide" or "lag") feature, where an initial digital value or analog control voltage is slowly transitioned to a new value over a period of time (see interpolation). Slew rate In electronics, slew rate is defined as the change of voltage or current, or any other electrical quantity, per unit of time. Expressed in SI units, the unit of measurement is volts/second or amperes/second or the unit

neg: Tonne Tonne The tonne () (Non-SI unit, symbol: t), commonly referred to as the metric ton in the United States, is a non-SI metric unit of mass equal to 1,000 kilograms; or one megagram (Mg); it is equivalent to approximately pounds, or 0.984 long tons (UK). Although not part of the SI, the tonne is accepted for use with SI units and prefixes by the International Committee for Weights and Measures. The tonne is derived from the weight of pure water; there are 1,000 litres in one tonne. The SI symbol for the tonne is "t", adopted at the same time

neg: Astronomical unit expanding outward from the Sun. This has led to calls to abandon the astronomical unit as a unit of measurement. As the speed of light has an exact defined value in SI units and the Gaussian gravitational constant "k" is fixed in the astronomical system of units, measuring the light time per unit distance is exactly equivalent to measuring the product "G" in SI units. Hence, it is possible to construct ephemerides entirely in SI units, which is increasingly becoming the norm. A 2004 analysis of radiometric measurements in the inner Solar System suggested that the secular increase in the

neg: Magnetic moment and external fields is not part of this internal energy. The unit for magnetic moment in terms of the International System of Units (SI) base units is A⋅m, where A is the ampere (the SI unit of current) and m is the meter (the SI unit of distance). This has equivalents in other units used in SI including: where N is the newton (the SI unit of force), T is the tesla (the SI unit of magnetic flux density), and J is the joule (the SI unit of energy). In the CGS system, there are several different sets of electromagnetism

neg: Rotation period between 1750 and 1892 was chosen in 1895 by Simon Newcomb as the independent unit of time in his Tables of the Sun. These tables were used to calculate the world's ephemerides between 1900 and 1983, so this second became known as the ephemeris second. The SI second was made equal to the ephemeris second in 1967. Earth's rotation period relative to the fixed stars, called its "stellar day" by the International Earth Rotation and Reference Systems Service (IERS), is seconds of mean solar time (UT1) Earth's rotation period relative to the precessing or moving mean vernal equinox, its "sidereal

neg: Kilowatt hour and megawatt refers to the entire thermal output, not the fraction which is converted to electricity. Kilowatt hour The kilowatt hour (symbol kWh, kW⋅h or kW h) is a unit of energy equal to 3.6 megajoules. If energy is transmitted or used at a constant rate (power) over a period of time, the total energy in kilowatt hours is equal to the power in kilowatts multiplied by the time in hours. The kilowatt hour is commonly used as a billing unit for energy delivered to consumers by electric utilities. The kilowatt hour (symbolized kW⋅h as per SI) is a composite

neg: Day unit of time in SI units. In 1967–68, during the 13th CGPM (Resolution 1), the International Bureau of Weights and Measures (BIPM) redefined a second as … the duration of 9 192 631 770 periods of the radiation corresponding to the transition between two hyperfine levels of the ground state of the caesium 133 atom. This makes the SI-based day last exactly 794 243 384 928 000 of those periods. Mainly due to tidal effects, the Earth's rotational period is not constant, resulting in minor variations for both solar days and stellar "days". The Earth's day has increased in length

neg: Speed of light other light sources. In 2011, the CGPM stated its intention to redefine all seven SI base units using what it calls "the explicit-constant formulation", where each "unit is defined indirectly by specifying explicitly an exact value for a well-recognized fundamental constant", as was done for the speed of light. It proposed a new, but completely equivalent, wording of the metre's definition: "The metre, symbol m, is the unit of length; its magnitude is set by fixing the numerical value of the speed of light in vacuum to be equal to exactly when it is expressed in the SI unit ."

neg: Radian Radian The radian (SI symbol rad) is the SI unit for measuring angles, and is the standard unit of angular measure used in many areas of mathematics. The length of an arc of a unit circle is numerically equal to the measurement in radians of the angle that it subtends; one radian is just under 57.3 degrees (expansion at ). The unit was formerly an SI supplementary unit, but this category was abolished in 1995 and the radian is now considered an SI derived unit. Separately, the SI unit of solid angle measurement is the steradian. The radian is most

neg: Energy It is equal to the energy expended (or work done) in applying a force of one newton through a distance of one metre. However energy is also expressed in many other units not part of the SI, such as ergs, calories, British Thermal Units, kilowatt-hours and kilocalories, which require a conversion factor when expressed in SI units. The SI unit of energy rate (energy per unit time) is the watt, which is a joule per second. Thus, one joule is one watt-second, and 3600 joules equal one watt-hour. The CGS energy unit is the erg and the imperial and US

neg: International System of Units derived quantities can be specified in terms of the SI base and derived units that have no named units in the SI system, such as acceleration, which is defined in SI units as m/s. The SI base units are the building blocks of the system and all the other units are derived from them. When Maxwell first introduced the concept of a coherent system, he identified three quantities that could be used as base units: mass, length and time. Giorgi later identified the need for an electrical base unit, for which the unit of electric current was chosen for SI.

neg: Frequency rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals (sound), radio waves, and light. For cyclical processes, such as rotation, oscillations, or waves, frequency is defined as a number of cycles per unit time. In physics and engineering disciplines, such as optics, acoustics, and radio, frequency is usually denoted by a Latin letter "f" or by the Greek letter "formula_1" or "ν" (nu) (see e.g. Planck's formula). The relation between the frequency and the period formula_2of a repeating event or oscillation is given by The SI derived unit of frequency is the hertz (Hz), named after the

neg: Year 365 or 366 days. In English, the abbreviations "y" and "yr" are commonly used. In astronomy, the Julian year is a unit of time; it is defined as 365.25 days of exactly 86,400 seconds (SI base unit), totalling exactly 31,557,600 seconds in the Julian astronomical year. The word "year" is also used for periods loosely associated with, but not identical to, the calendar or astronomical year, such as the seasonal year, the fiscal year, the academic year, etc. Similarly, "year" can mean the orbital period of any planet; for example, a Martian year and a Venusian year are examples of

neg: Radiant flux to measure: where < • > is the time-average. Radiant flux In radiometry, radiant flux or radiant power is the radiant energy emitted, reflected, transmitted or received, per unit time, and spectral flux or spectral power is the radiant flux per unit frequency or wavelength, depending on whether the spectrum is taken as a function of frequency or of wavelength. The SI unit of radiant flux is the watt (W), that is the joule per second () in SI base units, while that of spectral flux in frequency is the watt per hertz () and that of spectral flux in

neg: Attosecond Attosecond An attosecond is 1×10 of a second (one quintillionth of a second). For context, an attosecond is to a second what a second is to about 31.71 billion years. The word "attosecond" is formed by the prefix "atto" and the unit "second". "Atto-" was derived from the Danish word for eighteen ("atten"). Its symbol is as. An attosecond is equal to 1000 zeptoseconds, or of a femtosecond. Because the next higher SI unit for time is the femtosecond (10 seconds), durations of 10 s and 10 s will typically be expressed as tens or hundreds of attoseconds: Times which

neg: Attosecond can be expressed in attoseconds: Attosecond An attosecond is 1×10 of a second (one quintillionth of a second). For context, an attosecond is to a second what a second is to about 31.71 billion years. The word "attosecond" is formed by the prefix "atto" and the unit "second". "Atto-" was derived from the Danish word for eighteen ("atten"). Its symbol is as. An attosecond is equal to 1000 zeptoseconds, or of a femtosecond. Because the next higher SI unit for time is the femtosecond (10 seconds), durations of 10 s and 10 s will typically be expressed as tens or

neg: Theoretical astronomy were defined for continuity with ET and were based on what had become the standard SI second, which in turn had been derived from the measured second of ET. During the period 1991–2006, the TDB and TDT time scales were both redefined and replaced, owing to difficulties or inconsistencies in their original definitions. The current fundamental relativistic time scales are Geocentric Coordinate Time (TCG) and Barycentric Coordinate Time (TCB). Both of these have rates that are based on the SI second in respective reference frames (and hypothetically outside the relevant gravity well), but due to relativistic effects, their rates would

neg: Tonne as the unit in 1879. Its use is also official for the metric ton in the United States, having been adopted by the United States National Institute of Standards and Technology. It is a symbol, not an abbreviation, and should not be followed by a period. Informal and non-approved symbols or abbreviations include "T",”Te”, "mT", "MT", and "mt". Some of these are SI symbols for other units: "T" is the SI symbol for the tesla and "Mt" is the SI symbol for megatonne (equivalent to one teragram); if describing TNT equivalent units of energy, this is equivalent to 4.184 petajoules.

neg: Femtosecond Femtosecond A femtosecond is the SI unit of time equal to 10 or / of a second; that is, one quadrillionth, or one millionth of one billionth, of a second. For context, a femtosecond is to a second as a second is to about 31.71 million years; a ray of light travels approximately 0.3 µm (micrometers) in 1 femtosecond, a distance comparable to the diameter of a virus. The word "femtosecond" is formed by the SI prefix "femto" and the SI unit "second". Its symbol is fs. A femtosecond is equal to 1000 attoseconds, or 1/1000 picosecond. Because the next

neg: Picosecond Picosecond A picosecond is an SI unit of time equal to 10 or / (one trillionth) of a second. That is one trillionth, or one millionth of one millionth of a second, or 0.000 000 000 001 seconds. A picosecond is to one second as one second is to approximately 31,689 years. Multiple technical approaches achieve imaging within single-digit picoseconds: for example, the streak camera or intensified CCD (ICCD) cameras are able to picture the motion of light. The name is formed by the SI prefix "pico" and the SI unit "second". It is abbreviated as "ps". One picosecond is

neg: Femtosecond higher SI unit is 1000 times larger, times of 10 and 10 seconds are typically expressed as tens or hundreds of femtoseconds. Femtosecond A femtosecond is the SI unit of time equal to 10 or / of a second; that is, one quadrillionth, or one millionth of one billionth, of a second. For context, a femtosecond is to a second as a second is to about 31.71 million years; a ray of light travels approximately 0.3 µm (micrometers) in 1 femtosecond, a distance comparable to the diameter of a virus. The word "femtosecond" is formed by the SI prefix "femto"

neg: Kilogram force. Unfortunately, it is extremely difficult to develop a practical realization based upon accelerating masses. Experiments over a period of years in Japan with a superconducting, 30g mass supported by diamagnetic levitation never achieved an uncertainty better than ten parts per million. Magnetic hysteresis was one of the limiting issues. Other groups performed similar research that used different techniques to levitate the mass. Because SI prefixes may not be concatenated (serially linked) within the name or symbol for a unit of measure, SI prefixes are used with the unit "gram", not "kilogram", which already has a prefix as part of

neg: Candela per square metre Candela per square metre The candela per square metre (cd/m) is the derived SI unit of luminance. The unit is based on the candela, the SI unit of luminous intensity, and the square metre, the SI unit of area. Nit (nt) is a non-SI name also used for this unit (1 nt = 1 cd/m). The term "nit" is believed to come from the Latin word "nitere", to shine. As a measure of light emitted per unit area, this unit is frequently used to specify the brightness of a display device. The sRGB spec for monitors targets 80 cd/m. Typically,

neg: Angular velocity Angular velocity In physics, the angular velocity of a particle is the rate at which it rotates around a chosen center point: that is, the time rate of change of its angular displacement relative to the origin (i.e. in layman's terms: how quickly an object goes around something over a period of time - e.g. how fast the earth orbits the sun). It is measured in angle per unit time, radians per second in SI units, and is usually represented by the symbol omega (ω, sometimes Ω). By convention, positive angular velocity indicates counter-clockwise rotation, while negative is clockwise. For

neg: Astronomical constant frame of reference used. Values quoted in barycentric dynamical time (TDB) or equivalent time scales such as the "T" of the Jet Propulsion Laboratory ephemerides represent the mean values that would be measured by an observer on the Earth's surface (strictly, on the surface of the geoid) over a long period of time. The IAU also recommends values in SI units, which are the values which would be measured (in proper length and proper time) by an observer at the barycentre of the Solar System: these are obtained by the following transformations: The astronomical unit of time is a time

neg: Torque = r × F. Therefore, torque on a particle is "equal" to the first derivative of its angular momentum with respect to time. If multiple forces are applied, Newton's second law instead reads , and it follows that This is a general proof. Torque has dimension force times distance, symbolically . Official SI literature suggests using the unit "newton metre" (N⋅m) or the unit "joule per radian". The unit "newton metre" is properly denoted N⋅m or N m. This avoids ambiguity with mN, millinewtons. The SI unit for energy or work is the joule. It is dimensionally equivalent to a

neg: Roentgen (unit) absorbed dose in a wide range of matter. When measuring absorbed dose in a human due to external exposure, the SI unit the gray, or the related non-SI rad are used. From these can be developed the dose equivalents to consider biological effects from differing radiation types and target materials. These are equivalent dose, and effective dose for which the SI unit sievert or the non-SI rem are used. The following table shows radiation quantities in SI and non-SI units: Roentgen (unit) The roentgen or röntgen () (symbol R) is a legacy unit of measurement for the exposure of X-rays

neg: Horsepower-hour Horsepower-hour A horsepower-hour (hph or hp⋅h) is an outdated unit of energy, not used in the SI system of units. The unit represents an amount of work a horse is supposed capable of delivering during an hour (1 (one) horsepower integrated over a time interval of an hour). Based on differences in the definition of what constitutes the 'power of a horse', a horsepower-hour differs slightly from the German "Pferdestärkenstunde" (PSh): The horsepower-hour is still used in the railroad industry when sharing motive power (locomotives.) For example, if Railroad A borrows a 2,500 horsepower locomotive from Railroad B and operates

neg: Tonne a (now obsolete) force unit of the same name, the tonne-force, equivalent to about 9.8 kilonewtons: a unit also often called simply "tonne" or "metric ton" without identifying it as a unit of force. In contrast to the tonne as a mass unit, the tonne-force or metric ton-force is not acceptable for use with SI, partly because it is not an exact multiple of the SI unit of force, the newton. Tonne The tonne () (Non-SI unit, symbol: t), commonly referred to as the metric ton in the United States, is a non-SI metric unit of mass equal to 1,000

neg: Bit rate schemes, etc.) the "actual" bit rates used by some of the compared-to devices may be significantly higher than what is listed above. For example, telephone circuits using µlaw or A-law companding (pulse code modulation) yield 64 kbit/s. Bit rate In telecommunications and computing, bit rate (bitrate or as a variable "R") is the number of bits that are conveyed or processed per unit of time. The bit rate is quantified using the bits per second unit (symbol: "bit/s"), often in conjunction with an SI prefix such as "kilo" (1 kbit/s = 1,000 bit/s), "mega" (1 Mbit/s = 1,000 kbit/s), "giga"

neg: Coordinate time historical reasons Barycentric Dynamical Time (TDB), with a time unit that evaluates to SI seconds when observed from the Earth's surface, thus assuring that at least for several millennia TDB will remain within 2 milliseconds of Terrestrial Time (TT), albeit that the time unit of TDB, if measured by the hypothetical observer described above, at rest in the reference frame and at infinite distance, would be very slightly slower than the SI second (by 1 part in 1/L = 1 part in 10/1.550519768). Geocentric Coordinate Time (TCG) is based on a reference frame comoving with the geocenter (the center of

neg: Current density is the charge density (SI unit: coulombs per cubic metre), in which "n"(r, "t") is the number of particles per unit volume ("number density") (SI unit: m), "q" is the charge of the individual particles with density "n" (SI unit: coulombs). A common approximation to the current density assumes the current simply is proportional to the electric field, as expressed by: where E is the electric field and "σ" is the electrical conductivity. Conductivity "σ" is the reciprocal (inverse) of electrical resistivity and has the SI units of siemens per metre (S⋅m), and E has the SI units of newtons

neg: Gas constant "V" is the volume of gas (SI unit cubic metres), "n" is the amount of gas (SI unit moles), "m" is the mass (SI unit kilograms) contained in "V", and "T" is the thermodynamic temperature (SI unit kelvins). "R" is the molar-weight-specific gas constant, discussed below. The gas constant is expressed in the same physical units as molar entropy and molar heat capacity. From the general equation "PV" = "nRT" we get: where "P" is pressure, "V" is volume, "n" is number of moles of a given substance, and "T" is temperature. As pressure is defined as force per unit

neg: Horsepower-hour it for twelve hours, Railroad A owes a debt of (2,500 hp × 12 h) = 30,000 hp⋅h. Railroad A may repay the debt by loaning Railroad B a 3,000 horsepower locomotive for ten hours. Horsepower-hour A horsepower-hour (hph or hp⋅h) is an outdated unit of energy, not used in the SI system of units. The unit represents an amount of work a horse is supposed capable of delivering during an hour (1 (one) horsepower integrated over a time interval of an hour). Based on differences in the definition of what constitutes the 'power of a horse', a horsepower-hour differs

neg: Rotation period day", is seconds of mean solar time (UT1) Thus the sidereal day is shorter than the stellar day by about 8.4 ms. The length of the mean solar day in SI seconds is available from the IERS for the periods 1623–2005 and 1962–2005. Recently (1999–2005) the average annual length of the mean solar day in excess of 86400 SI seconds has varied between 0.3 ms and 1 ms, which must be added to both the stellar and sidereal days given in mean solar time above to obtain their lengths in SI seconds. Rotation period In astronomy, the rotation period of

neg: Linear motion unit of acceleration is formula_19 or metre per second squared. If formula_20 is the average acceleration and formula_21 is the average velocity over the time interval formula_9 then mathematically, formula_23 The instantaneous acceleration is the limit of the ratio formula_24 and formula_9 as formula_9 approaches zero i.e., formula_27 formula_28 The rate of change of acceleration, the third derivative of displacement is known as jerk. The SI unit of jerk is formula_29. In the UK jerk is also known as jolt. The rate of change of jerk, the fourth derivative of displacement is known as jounce. The SI unit of jounce

neg: Candela per square metre calibrated monitors should have a brightness of 120 cd/m. Most consumer desktop liquid crystal displays have luminances of 200 to 300 cd/m. High-definition televisions range from 450 to about 1500 cd/m. One candela per square metre is equal to: Candela per square metre The candela per square metre (cd/m) is the derived SI unit of luminance. The unit is based on the candela, the SI unit of luminous intensity, and the square metre, the SI unit of area. Nit (nt) is a non-SI name also used for this unit (1 nt = 1 cd/m). The term "nit" is believed to

neg: Radiant flux Radiant flux In radiometry, radiant flux or radiant power is the radiant energy emitted, reflected, transmitted or received, per unit time, and spectral flux or spectral power is the radiant flux per unit frequency or wavelength, depending on whether the spectrum is taken as a function of frequency or of wavelength. The SI unit of radiant flux is the watt (W), that is the joule per second () in SI base units, while that of spectral flux in frequency is the watt per hertz () and that of spectral flux in wavelength is the watt per metre ()—commonly the watt

neg: Centimetre–gram–second system of units usage consistent with the SI system. In mechanics, the CGS and SI systems of units are built in an identical way. The two systems differ only in the scale of two out of the three base units (centimetre versus metre and gram versus kilogram, respectively), while the third unit (second as the unit of time) is the same in both systems. There is a one-to-one correspondence between the base units of mechanics in CGS and SI, and the laws of mechanics are not affected by the choice of units. The definitions of all derived units in terms of the three

neg: Metric time have a formal name. The only way to express a nonstandard order of magnitude as an SI unit is to combine two prefixed SI derived units whose component base units cancel out; for example, units of 10 seconds could be expressed as "kilojoules per centiwatt" (kJ/cW) or "hectocoulombs per milliampere" (hC/mA). Such misuse of SI derived units can create a cognitive dissonance; to do so requires the invocation of units not directly related to the quantity being measured (coulombs and amperes, for example, quantify electricity, making it awkward to combine the two in a way that creates a unit of

neg: Hertz The dimension of the unit hertz is 1/time (1/T). Expressed in base SI units it is 1/second (1/s). In English, "hertz" is also used as the plural form. As an SI unit, Hz can be prefixed; commonly used multiples are kHz (kilohertz, 10 Hz), MHz (megahertz, 10 Hz), GHz (gigahertz, 10 Hz) and THz (terahertz, 10 Hz). One hertz simply means "one cycle per second" (typically that which is being counted is a complete cycle); 100 Hz means "one hundred cycles per second", and so on. The unit may be applied to any periodic event—for example, a clock might be

neg: International System of Units unsuitable for precision measurements of a property of a body, and this makes a unit of weight unsuitable as a base unit. The derived units in the SI are formed by powers, products or quotients of the base units and are unlimited in number. Derived units are associated with derived quantities; for example, velocity is a quantity that is derived from the base quantities of time and length, and thus the SI derived unit is metre per second (symbol m/s). The dimensions of derived units can be expressed in terms of the dimensions of the base units. Combinations of base

neg: Mass versus weight of Units (SI), the kilogram is the basic unit of mass, and the newton is the basic unit of force. The non-SI kilogram-force is also a unit of force typically used in the measure of weight. Similarly, the avoirdupois pound, used in both the Imperial system and U.S. customary units, is a unit of mass, and its related unit of force is the pound-force. When an object's weight (its gravitational force) is expressed in "kilograms", this actually refers to the kilogram-force (kgf or kg-f), also known as the "kilopond" (kp), which is a non-SI unit of force. All objects on

neg: SI derived unit SI derived unit SI derived units are units of measurement derived from the seven base units specified by the International System of Units (SI). They are either dimensionless or can be expressed as a product of one or more of the base units, possibly scaled by an appropriate power of exponentiation. The SI has special names for 22 of these derived units (for example, hertz, the SI unit of measurement of frequency), but the rest merely reflect their derivation: for example, the square metre (m), the SI derived unit of area; and the kilogram per cubic metre (kg/m or kg

neg: Tog (unit) G in W/mK then a handy backronym for remembering what Tog means is "10/G", or "Ten Over G." Tog (unit) The tog is a measure of thermal insulance of a unit area, also known as thermal resistance. It is commonly used in the textile industry and often seen quoted on, for example, duvets and carpet underlay. The Shirley Institute in Manchester, England developed the tog as an easy-to-follow alternative to the SI unit of mK/W. The name comes from the informal word "togs" for 'clothing', which itself was probably derived from the word "toga", a Roman garment. The basic unit

neg: Spectral power distribution the incident wavelength. Mathematically, for the spectral power distribution of a radiant exitance or irradiance one may write: where "M"("λ") is the spectral irradiance (or exitance) of the light (SI units: W/m = kg·m·s); "Φ" is the radiant flux of the source (SI unit: watt, W); "A" is the area over which the radiant flux is integrated (SI unit: square meter, m); and "λ" is the wavelength (SI unit: meter, m). (Note that it is more convenient to express the wavelength of light in terms of nanometers; spectral exitance would then be expressed in units of W·m·nm.) The approximation is

neg: Siemens (unit) of Units (SI)" refers to the mho as an "unaccepted special name for an SI unit", and indicates that it should be strictly avoided. The SI term "siemens" is used universally in science and often in electrical applications, while "mho" is still used in some electronic contexts. The inverted capital omega symbol, while not an official SI abbreviation, is less likely to be confused with a variable than the letter S when doing algebraic calculations by hand, where the usual typographical distinctions (such as italic for variables and Roman for unit names) are difficult to maintain. Likewise, it is difficult

neg: Rutherford (unit) unit for activity, the rutherford became obsolete, and it is no longer commonly used. The following table shows radiation quantities in SI and non-SI units: Rutherford (unit) The rutherford (symbol Rd) is a non-SI unit of radioactive decay. It is defined as the activity of a quantity of radioactive material in which one million nuclei decay per second. It is therefore equivalent to one megabecquerel, and one becquerel equals one microrutherford. One rutherford is equivalent to 2.703 × 10 curie. The unit was introduced in 1946. It was named after British/New Zealand physicist and Nobel laureate Lord Ernest Rutherford (Nobel

neg: Weight 30 pounds-force when visiting the Moon. In most modern scientific work, physical quantities are measured in SI units. The SI unit of weight is the same as that of force: the newton (N) – a derived unit which can also be expressed in SI base units as kg⋅m/s (kilograms times meters per second squared). In commercial and everyday use, the term "weight" is usually used to mean mass, and the verb "to weigh" means "to determine the mass of" or "to have a mass of". Used in this sense, the proper SI unit is the kilogram (kg). In United States

neg: Centimetre–gram–second system of units Units (SI). In many fields of science and engineering, SI is the only system of units in use but there remain certain subfields where CGS is prevalent. In measurements of purely mechanical systems (involving units of length, mass, force, energy, pressure, and so on), the differences between CGS and SI are straightforward and rather trivial; the unit-conversion factors are all powers of 10 as and . For example, the CGS unit of force is the dyne which is defined as , so the SI unit of force, the newton (), is equal to 100,000 dynes. On the other hand, in

neg: Darcy's law for multiphase flow the fluid components involved. The above equations are written in SI units and we are assuming that all material properties are also defined within the SI units. A result of this is that above versions of the equations do not need any unit conversion constants. The petroleum industry applies a variety of units, of which a least two have some prevalence. If you want to apply units other than SI units, you must establish correct unit conversion constants for the multiphase flow equations. The above equations are written in SI units (short SI) suppressing that the unit D (darcy) for

neg: Voltameter Voltameter A voltameter or coulometer is a scientific instrument used for measuring quantity of electricity (electric charge) through electrolytic action. The SI unit of quantity of electricity is the coulomb. The voltameter should not be confused with a voltmeter, which measures electric potential. The SI unit for electric potential is the volt. The voltameter is an electrolytic cell and the measurement is made by weighing the element deposited or released at the cathode in a specified time. This is the most accurate type. It consists of two silver plates in a solution of silver nitrate. When current is flowing, silver

neg: Orders of magnitude (mass) Orders of magnitude (mass) To help compare different orders of magnitude, the following lists describe various mass levels between 10 kg and 10 kg. The table below is based on the kilogram (kg), the base unit of mass in the International System of Units (SI). The kilogram is the only standard unit to include an SI prefix ("kilo-") as part of its name. The "gram" (10 kg) is an SI derived unit of mass. However, the "names" of all SI mass units are based on "gram", rather than on "kilogram"; thus 10 kg is a "megagram" (10 g), not a

neg: Viscosity develop and maintain the properties of the drilling fluid to the specifications required. The SI unit of dynamic viscosity is Pa·s or kg·m·s. The cgs unit is called the poise (P), named after Jean Léonard Marie Poiseuille. It is commonly expressed, particularly in ASTM standards, as "centipoise" (cP) since the latter is equal to the SI multiple millipascal seconds (mPa·s). The SI unit of kinematic viscosity is m/s, whereas the cgs unit for kinematic viscosity is the "stokes" (St), named after Sir George Gabriel Stokes. It is sometimes expressed in terms of "centistokes" (cSt). In U.S. usage, "stoke" is sometimes

neg: Degree (angle) Degree (angle) A degree (in full, a degree of arc, arc degree, or arcdegree), usually denoted by ° (the degree symbol), is a measurement of a plane angle, defined so that a full rotation is 360 degrees. It is not an SI unit, as the SI unit of angular measure is the radian, but it is mentioned in the SI brochure as an accepted unit. Because a full rotation equals 2 radians, one degree is equivalent to radians. The original motivation for choosing the degree as a unit of rotations and angles is unknown. One theory states that it is

neg: Picosecond equal to 1000 femtoseconds, or 1/1000 nanoseconds. Because the next SI unit is 1000 times larger, measurements of 10 and 10 second are typically expressed as tens or hundreds of picoseconds. Some notable measurements in this range include: Picosecond A picosecond is an SI unit of time equal to 10 or / (one trillionth) of a second. That is one trillionth, or one millionth of one millionth of a second, or 0.000 000 000 001 seconds. A picosecond is to one second as one second is to approximately 31,689 years. Multiple technical approaches achieve imaging within single-digit picoseconds: for example,

neg: SI derived unit Until 1995, the SI classified the radian and the steradian as "supplementary units", but this designation was abandoned and the units were grouped as derived units. SI derived unit SI derived units are units of measurement derived from the seven base units specified by the International System of Units (SI). They are either dimensionless or can be expressed as a product of one or more of the base units, possibly scaled by an appropriate power of exponentiation. The SI has special names for 22 of these derived units (for example, hertz, the SI unit of measurement of frequency), but the

neg: MKS system of units that since the derived units (like joules) are based on MKS units, using MKS units naturally gives answers in the appropriate SI unit. For example, the kinetic energy of an object is defined by . If the calculation is done in MKS units of kilogram and meters per second then the result is in joules, the SI unit for energy. If the same calculation is done using CGS units the answer is in ergs (). The exact list of units used in the MKS system changed over time. It incorporated base units other than the metre, kilogram, and second in

neg: Spectroradiometer (SI unit: meter, m), incident on the surface area, formula_5 (SI unit: square meter,m²). The SI unit for spectral irradiance is W/m. However it is often more useful to measure area in terms of centimeters and wavelength in nanometers, thus submultiples of the SI units of spectral irradiance will be used, for example μW/cm*nm Spectral irradiance will vary from point to point on the surface in general. In practice, it is important note how radiant flux varies with direction, the size of the solid angle subtended by the source at each point on the surface, and the orientation of the

neg: Cross section (physics) not azimuthally symmetric, such as when the beam or target particles possess magnetic moments oriented perpendicular to the beam axis, the differential cross section must also be expressed as a function of the azimuthal angle. For scattering of particles of incident flux off a stationary target consisting of many particles, the differential cross section at an angle is related to the flux of scattered particle detection in particles per unit time by Here is the finite angular size of the detector (SI unit: sr), is the number density of the target particles (SI units: m), and is the thickness of

neg: Darcy's law for multiphase flow the absolute permeability is defined in non-SI units. That is way there are no unit-related constants. The petroleum industry don't use the SI units. Instead they use a special version of SI units that we will call Applied SI units, or they use another set of units called Field units which has its origin from USA and UK. Temperature is not included in the equations, so we can use the factor-label method (also called unit-factor method) which says that if we have a variable/parameter with unit H, we multiply this variable/parameter by a conversion constant C and then the variable

neg: Coordinate time the Earth), and is defined in principle for use for calculations concerning phenomena on or in the region of the Earth, such as planetary rotation and satellite motions. To a much smaller extent than with TCB compared with TDB, but for a corresponding reason, the SI second of TCG when observed from the Earth's surface shows a slight acceleration on the SI seconds realized by Earth-surface-based clocks. Accordingly, Terrestrial Time (TT) has also been defined as a scaled version of TCG, with the scaling such that on the defined geoid the unit rate is equal to the SI second, albeit

neg:
Barrer SI units: formula_5 Barrer Barrer is a non-SI unit of gas permeability (specifically, gas permeability) used in the membrane technology and contact lens industry. It is named after Richard Barrer. formula_1 Here the 'cm' is standard cubic centimeter, which is a unit of amount of gas rather than a unit of volume. It represents the amount of gas molecules or moles that "would" occupy one cubic centimeter at standard temperature and pressure, as calculated via the ideal gas law.
 In SI unit Barrer can be expressed as:
 formula_2
 The cm corresponds in the permeability equations to the

neg: Katal name "katal" has been used for decades, and the unit became an official SI unit in 1999. The name comes from the Ancient Greek κατάλυσις ("katalysis"), meaning "dissolution", which is the same origin as the word "catalysis" itself comes from. Katal The katal (symbol: kat) is the unit of catalytic activity in the International System of Units (abbreviated SI). It is a derived SI unit for quantifying the catalytic activity of enzymes (that is, measuring the enzymatic activity level in enzyme catalysis) and other catalysts. The General Conference on Weights and Measures and other international organizations recommend use of the

neg: Concentration SI unit is kg/m (equal to g/L). The molar concentration formula_5 is defined as the amount of a constituent formula_6 (in moles) divided by the volume of the mixture formula_3: The SI unit is mol/m. However, more commonly the unit mol/L (= mol/dm) is used. The number concentration formula_9 is defined as the number of entities of a constituent formula_10 in a mixture divided by the volume of the mixture formula_3: The SI unit is 1/m. The volume concentration formula_13 (not to be confused with volume fraction) is defined as the volume of a constituent formula_14 divided by the volume

neg: Metre per second Metre per second Metre per second (American English: meter per second) is an SI derived unit of both speed (scalar) and velocity (vector quantity which specifies both magnitude and a specific direction), defined by distance in metres divided by time in seconds. The SI unit symbols are m·s, m s, m/s, or , sometimes (unofficially) abbreviated as . Where metres per second are several orders of magnitude too slow to be convenient, such as in astronomical measurements, velocities may be given in kilometres per second, where is 1000 metres per second, sometimes unofficially abbreviated as "kps". is equivalent to: 1

neg: Centimetre–gram–second system of units in the practical system and are the same as the SI units. However, intensive properties (that is, anything that is per unit length, area, or volume) will not be the same as SI since the cgs unit of distance is the centimetre. For instance electric field strength is in units of volts per centimetre, magnetic field strength is in oersteds and resistivity is in ohm-cm. Some physicists and electrical engineers in North America still use these hybrid units. There were at various points in time about half a dozen systems of electromagnetic units in use, most based on the CGS

neg: Sound energy density Sound energy density Sound energy density or sound density is the sound energy per unit volume. The SI unit of sound energy density is the pascal (Pa), that is the joule per cubic metre (J/m) in SI based units. Sound energy density, denoted "w", is defined by where The terms instantaneous energy density, maximum energy density, and peak energy density have meanings analogous to the related terms used for sound pressure. In speaking of average energy density, it is necessary to distinguish between the space average (at a given instant) and the time average (at a given point). The sound

neg: Collective dose is assumed that population sizes and behaviour remain the same for all time. The SI unit for Collective dose, S, is man-sieverts. The person-rem is sometimes used as the non SI unit in some regulatory systems. Atmospheric nuclear weapons tests in isolated areas often resulted in doses of less than 1 mSv to any individual. All the thousands of atmospheric tests that occurred in the 20th century together now cause a 30,000 man-Sv collective dose each year from fallout. The annual dose reduces each year. Collective dose The collective effective dose, dose quantity S, is calculated as the sum of

neg: Dvaravati Dvaravati The Dvaravati (, ; - "Tvearvottey") period lasted from around the 6th to the 11th century in what is now Thailand. Dvaravati refers to a culture, an art style, and a disparate conglomerate of principalities. Archaeological research over the past two decades or so has revealed the presence of a "proto-Dvaravati" period which spans the 4th-5th century, and perhaps earlier. The culture of Dvaravati, was based around moated cities, the earliest of which appears to be U Thong, in modern day Suphanburi province. Other key sites include Nakhon Pathom, Phong Tuk, Si Thep, Khu Bua and Si Mahosot amongst

neg: Gray (unit) of the gray by the 15th General Conference on Weights and Measures as the unit of measure of the absorption of ionizing radiation, specific energy absorption, and of kerma in 1975 was the culmination of over half a century of work, both in the understanding of the nature of ionizing radiation and in the refinement of measuring techniques. The following table shows radiation quantities in SI and non-SI units. Gray (unit) The gray (symbol: Gy) is a derived unit of ionizing radiation dose in the International System of Units (SI). It is defined as the absorption of one joule of

neg: Unit of measurement the International System of Units, or SI. There are seven SI base units. All other SI units can be derived from these base units. For most quantities a unit is necessary to communicate values of that physical quantity. For example, conveying to someone a particular length without using some sort of unit is impossible, because a length cannot be described without a reference used to make sense of the value given. But not all quantities require a unit of their own. Using physical laws, units of quantities can be expressed as combinations of units of other quantities. Thus only a

neg: Gaussian units A number of the units defined by the table have different names but are in fact dimensionally equivalent—i.e., they have the same expression in terms of the base units cm, g, s. (This is analogous to the distinction in SI between becquerel and Hz, or between newton metre and joule.) The different names help avoid ambiguities and misunderstandings as to what physical quantity is being measured. In particular, "all" of the following quantities are dimensionally equivalent in Gaussian units, but they are nevertheless given different unit names as follows: Any formula can be converted between Gaussian and SI units by

neg: Unit of length Unit of length A unit of length refers to any discrete, pre-established length or distance having a constant magnitude which is used as a reference or convention to express linear dimension. The most common units in modern use are U.S. customary units in the United States and metric units elsewhere. British Imperial units are still used for some purposes in the United Kingdom and some other countries. The metric system is sub-divided into SI and non-SI units. The base unit in the International System of Units (SI) is the metre, defined as "the length of the path travelled by light

neg: Hand (unit) Hand (unit) The hand is a non-SI unit of measurement of length standardized to . It is used to measure the height of horses in some English-speaking countries, including Australia, Canada, the Republic of Ireland, the United Kingdom and the United States. It was originally based on the breadth of a human hand. The adoption of the international inch in 1959 allowed for a standardized imperial form and a metric conversion. It may be abbreviated to "h" or "hh". Although measurements between whole hands are usually expressed in what appears to be decimal format, the subdivision of the hand is

neg: Gaussian units to foot–pound–second gaussian units. The main alternative to the Gaussian unit system is SI units, historically also called the MKSA system of units for metre–kilogram–second–ampere. The Gaussian unit system is just one of several electromagnetic unit systems within CGS. Others include "electrostatic units", "electromagnetic units", and Lorentz–Heaviside units. Some other unit systems are called "natural units", a category that includes atomic units, Planck units, and others. SI units are by far the most common today. In engineering and practical areas, SI is nearly universal and has been for decades. In technical, scientific literature (such as theoretical physics and astronomy), Gaussian

neg: Rad (unit) the SI. The US NIST clarified in 1998 that it was providing its own interpretations of the SI system, whereby it accepted the rad for use in the US with the SI, while recognizing that the CIPM did not. NIST recommends defining the rad in relation to SI units in every document where this unit is used. Nevertheless, use of the rad remains widespread in the US, where it is still an industry standard. Although the United States Nuclear Regulatory Commission still permits the use of the units curie, rad, and rem alongside SI units, the European Union required that

neg: SI derived unit m), the SI derived unit of density. The names of SI derived units, when written in full, are in lowercase. However, the symbols for units named after persons are written with an uppercase initial letter. For example, the symbol for hertz is "Hz"; but the symbol for metre is "m". The International System of Units assigns special names to 22 derived units, which includes two dimensionless derived units, the radian (rad) and the steradian (sr). Some other units such as the hour, litre, tonne, bar and electronvolt are not SI units, but are widely used in conjunction with SI units.