System of Units: MKS, CGS and SI

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<–2/”>a >Measurement of any physical quantity involves comparison with a certain basic, arbitrarily chosen, internationally accepted reference standard called unit. The result of a measurement of a physical quantity is expressed by a number (or numerical measure) accompanied by a unit.

A unit of measurement is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same quantity. Any other value of that quantity can be expressed as a simple multiple of the unit of measurement. For example, length is a physical quantity.
Four different systems of units are commonly used in science and engineering. The difference among them arises from the difference in the units used to represent the three fundamental quantities, namely length (l), mass (m) and time (t).
The base units for length, mass and time in these systems were as follows :
• In CGS system they were centimetre, gram and second respectively.
• In FPS system they were foot, pound and second respectively.
• In MKS system they were metre, kilogram and second respectively

SI Units

SI Base Units

Base quantity Name Symbol
length meter m
mass kilogram kg
time second s
electric current ampere A
thermodynamic temperature kelvin K
amount of substance mole mol
luminous intensity candela cd

SI Derived Units:-

area square meter m2
volume cubic meter m3
speed, velocity meter per second m/s
acceleration meter per second squared m/s2
wave number reciprocal meter m-1
mass density kilogram per cubic meter kg/m3
specific volume cubic meter per kilogram m3/kg
current density ampere per square meter A/m2
Magnetic Field strength ampere per meter A/m
amount-of-substance concentration mole per cubic meter mol/m3
luminance candela per square meter cd/m2

MKS System

MKS unit of measurement is meter-kilogram-second. SI unit was derived from MKS system. In MKS system length is in meter (m), area is in square meter (m2 ), volume is in cubic meter (m3 ), time in second (s), mass is in kilogram (kg), weight (force) is in kilogram-meter per second square (kg-m/s2 ), density is in kilogram per centimeter square (kg/cm2 ), acceleration is in kilogram-meter per second square (kgm/s2 ), force(pressure) is in kilogram-force per square centimeter (kgf/cm2 ).

CGS System

The CGS system was introduced formally by the British Association for the Advancement of Science in 1874. It found almost immediate favor with working scientists, and it was the system most commonly used in scientific work for many years. Meanwhile, the further development of the metric system was based on meter and kilogram standards created and distributed in 1889 by the International Bureau of Weights and Measures (BIPM). During the 20th century, metric units based on the meter and kilogram–the MKS units–were used more and more in commercial transactions, engineering, and other practical areas.

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The International System of Units (SI) is the modern form of the metric system, and is the most widely used system of measurement in the world. It is a decimal system, which means that it is based on the number 10. The SI system is made up of seven base units, which are:

  • The metre (m), which is the unit of length.
  • The kilogram (kg), which is the unit of mass.
  • The second (s), which is the unit of time.
  • The ampere (A), which is the unit of electric current.
  • The kelvin (K), which is the unit of temperature.
  • The mole (mol), which is the unit of amount of substance.
  • The candela (cd), which is the unit of luminous intensity.

In addition to the seven base units, there are also a number of derived units, which are formed by combining the base units in various ways. For example, the unit of speed is the metre per second (m/s), which is the distance travelled in one second.

The SI system is a coherent system, which means that the units are related to each other in a consistent way. For example, the speed of Light in a vacuum is 299,792,458 metres per second. This means that if you divide the distance of one light-year (9.4607 × 1012 km) by the time it takes light to travel that distance (365.25 days × 24 hours × 60 minutes × 60 seconds), you will get the speed of light in metres per second.

The SI system is also a practical system, which means that it is easy to use and understand. The base units are all defined in terms of easily observable phenomena, such as the metre, which is defined as the distance that light travels in a vacuum in 1/299,792,458 of a second.

The SI system is constantly being updated to reflect new scientific discoveries and technological advances. For example, in 2019, the definition of the kilogram was changed to be based on the fundamental constant of Planck’s constant, rather than on a physical object.

The SI system is the official system of measurement in most countries around the world. It is also the preferred system of measurement for scientific and technical work.

The MKS system is a system of measurement that is based on the metre, kilogram, and second. It is a subset of the SI system, and is used in many countries around the world.

The CGS system is a system of measurement that is based on the centimetre, gram, and second. It is an older system of measurement that is still used in some countries, but is being replaced by the SI system.

The SI system is a more modern and accurate system of measurement than the MKS or CGS systems. It is also more widely used, and is the preferred system of measurement for scientific and technical work.

What is a system of units?

A system of units is a collection of units of measurement that are used to quantify physical quantities. The most common system of units is the International System of Units (SI), which is based on the metre, kilogram, second, ampere, kelvin, mole, and candela.

What are the different types of systems of units?

There are many different systems of units, but the most common are the International System of Units (SI), the CGS system, and the MKS system. The SI system is the most widely used system of units in the world, and it is based on the metre, kilogram, second, ampere, kelvin, mole, and candela. The CGS system is a metric system that is based on the centimetre, gram, and second. The MKS system is a metric system that is based on the metre, kilogram, and second.

What are the advantages and disadvantages of different systems of units?

The SI system is the most widely used system of units in the world, and it is based on the metre, kilogram, second, ampere, kelvin, mole, and candela. The SI system is a decimal system, which makes it easy to convert between units. The SI system is also a coherent system, which means that the units are related to each other in a simple way. The CGS system is a metric system that is based on the centimetre, gram, and second. The CGS system is a convenient system of units for many scientific and engineering applications. However, the CGS system is not as widely used as the SI system. The MKS system is a metric system that is based on the metre, kilogram, and second. The MKS system is a convenient system of units for many scientific and engineering applications. However, the MKS system is not as widely used as the SI system.

What is the history of systems of units?

The history of systems of units is a long and complex one. The first systems of units were developed in ancient Egypt and Babylonia. These early systems of units were based on the human body, such as the cubit, which was the length of a forearm. Over time, more and more systems of units were developed, each with its own advantages and disadvantages. In the 18th century, the metric system was developed in France. The metric system is a decimal system, which makes it easy to convert between units. The metric system is also a coherent system, which means that the units are related to each other in a simple way. The metric system quickly became the most widely used system of units in the world. In the 20th century, the International System of Units (SI) was developed. The SI system is based on the metric system, but it has been updated to include more modern units. The SI system is now the most widely used system of units in the world.

What are the future trends in systems of units?

The future trends in systems of units are difficult to predict. However, it is likely that the SI system will continue to be the most widely used system of units in the world. It is also possible that new systems of units will be developed in the future, to meet the needs of new technologies.

  1. The SI unit of mass is:
    (a) kilogram (kg)
    (b) gram (g)
    (c) milligram (mg)
    (d) centigram (cg)

  2. The SI unit of length is:
    (a) meter (m)
    (b) centimeter (cm)
    (c) millimeter (mm)
    (d) kilometer (km)

  3. The SI unit of time is:
    (a) second (s)
    (b) minute (min)
    (c) hour (h)
    (d) day (d)

  4. The SI unit of temperature is:
    (a) degree Celsius (°C)
    (b) degree Fahrenheit (°F)
    (c) kelvin (K)
    (d) none of the above

  5. The SI unit of speed is:
    (a) meter per second (m/s)
    (b) kilometer per hour (km/h)
    (c) both (a) and (b)
    (d) none of the above

  6. The SI unit of acceleration is:
    (a) meter per second squared (m/s2)
    (b) kilometer per hour squared (km/h2)
    (c) both (a) and (b)
    (d) none of the above

  7. The SI unit of force is:
    (a) newton (N)
    (b) dyne
    (c) both (a) and (b)
    (d) none of the above

  8. The SI unit of pressure is:
    (a) pascal (Pa)
    (b) bar
    (c) both (a) and (b)
    (d) none of the above

  9. The SI unit of energy is:
    (a) joule (J)
    (b) calorie
    (c) both (a) and (b)
    (d) none of the above

  10. The SI unit of power is:
    (a) watt (W)
    (b) horsepower
    (c) both (a) and (b)
    (d) none of the above

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