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Rev. Notes > AS > Physical quantities and units
Previous Topic Physical quantities and units Next Topic



Areas of Physics

Interdisciplanary areas of physics

Quantities in Physics

Base Units

Convention for indicating units

Derived Units

S.I. Units (International System of Units)

Supplementary units

Homogeneity of equations

Significant figures

Rules of Significant figures

Further discussion on Significant figures


Scientific notation

The Avogadro's Constant

Scalars and Vectors

Addition and subtraction of co-planar vectors

Rectangular components of a vector


S.I. Units (International System of Units)

In 1960, an international committee agreed on a set of definitions and standard to describe the physical quantities. The system that was established is called the system international (SI).

Due to the simplicity and convenience with which the units in this system are amendable to arithmetical manipulation, it is in universal use by the world’s scientific community and by most nations. The system international (SI) is built up from three kinds of units: base units, Supplementary units and derived units.

S.I. Base Units

Base Quantity Name Symbol
Length meter m
Mass kilogram kg
Time seconds s
Electric current ampere A
Tempearture kelvin k
Amount of substance mole mol
Luminous intensity candela cd

S.I. Derived Units

Derived Quantity Name Symbol Equivalent S.I. Units
Frequency hertz Hz S-1
Force newton N m.Kg.S-2
Pressure pascal Pa N.m-2
Energy joule J N.m
Power watt W Js-1
Electric charge coulomb C A.s
Electric potential volt V W.A-1
Electric resistance ohm Ω V.A-1
Temperature degree celsius oC k

S.I. Prefixes

Name Factor Symbol Numerical value
tera 1012 T 1 000 000 000 000
giga 109 G 1 000 000 000
mega 106 M 1 000 000
kilo 103 k 1 000
hecto 102 h 1 00
deka 101 da 10
deci 10-1 d 0.1
centi 10-2 c 0.01
milli 10-3 m 0.001
micro 10-6 µ 0.000 001
nano 10-9 n 0.000 000 001
pico 10-12 p 0.000 000 000 001


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Student Said :

Super i got so much of information through

  11/07/15 09:09 AM
Kennyworthy Mphande Said :
nicely explained.
  26/01/15 07:00 PM
benard wilson Said :
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  10/09/14 09:57 PM
muhammad fawad Said :
nice writting..
  06/05/14 06:47 PM


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