Derived Units

Derived Units

"The units of derived physical quantities which are derived from basic units or fundamental units are called derived units."


Rules for writing SI units
i) Full name of the unit always starts with small letter even if named after a person. e.g. Newton, joule and not Newton, Joule.
ii) A symbol for unit named after a person should be in capital letters e.g. 'N' for Newton, joule and not Newton, Joule.
iii) Symbols for all other units are written in small letters. e.g. 'm' for a meter,'s' for second etc.
iv) Symbols of units are not to be expressed in plural form. e.g. 25 m and not 25 ms.
v) Full stop and any other punctuation mark should not be written after the symbols e.g. kg and not kg or N and not N.

Table of some SI derived units expressed in SI base unit

Sr. No.
Physical Quality
Name of SI Unit
Symbol
1
Area
Square meter
m2
2
Volume
Cubic meter
m3
3
Density
Kilogram per cubic meter
Kg/m3
4
Speed / Velocity
Meter per second
m/s
5
Acceleration
Meter per second square
m/s2
6
Momentum
Kilogram meter per second
Kg m/s
7
Force
Newton
N
8
Impulse
Newton second
Ns
9
Work
Joule
J
10
Kinetic Energy
Joule
J
11
Potential Energy
Joule
J
12
Power
Joule per second or watt
J/s or W
13
Pressure
Newton per square meter
N/m2

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