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# Unit And Measurement - Physics, IAS UPSC Notes | EduRev

## UPSC : Unit And Measurement - Physics, IAS UPSC Notes | EduRev

The document Unit And Measurement - Physics, IAS UPSC Notes | EduRev is a part of the UPSC Course General Science(Prelims) by IRS Divey Sethi.
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Unit And Measurement

Unit

A unit is a particular physical quantity, defined and adopted by convention, with which other particular quantities of the same kind are compared to express their value.

THE INTERNATIONAL SYSTEM OF UNITS

In earlier time scientists of different countries were using different systems of units for measurement.

• 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.

• The system of units which is at present internationally accepted for measurement is the Système Internationale d’ abbreviated as SI.
• The SI was developed and recommended by General Conference on Weights and Measures in 1971 for international usage in scientific, technical, industrial and commercial work.

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

Units of long distance

• Light year = distance travelled by the light in one year = 1016m
• Parsec (Parallactic second) is the distance corresponding to a parallax of one second of arc,
• 1 Parsec = 3.26 light year

 Name deca- hecto- kilo- mega- giga- tera- peta- exa- zetta- yotta- Prefix da h k M G T P E Z Y Factor 101 102 103 106 109 1012 1015 1018 1021 1024

Units of long distance

• Light year = distance travelled by the light in one year = 1016m
• Parsec (Parallactic second) is the distance corresponding to a parallax of one second of arc,
• 1 Parsec = 3.26 light year
 Name deca- hecto- kilo- mega- giga- tera- peta- exa- zetta- yotta- Prefix da h k M G T P E Z Y Factor 101 102 103 106 109 1012 1015 1018 1021 1024

Unit of short distance

 Name deci- centi- milli- micro- nano- pico- femto- atto- zepto- yocto- Prefix d c m μ n p f a z y Factor 10−1 10−2 10−3 10−6 10−9 10−12 10−15 10−18 10−21 10−24

Mass & Weight

• Mass is defined as the amount of matter an object has. One of the qualities of mass is that it has inertia Mass is a measure of how much inertia an object shows.
• The weight of an object on earth depends on the force of attraction (gravity) between the object and earth.
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## General Science(Prelims) by IRS Divey Sethi

39 videos|110 docs|255 tests

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