System of Units
There are four system of units available namely – MKS System, CGS System, FPS System, and SI system.
MKS System: The full form of MKS System is Metre Kilogram Second. In MKS system, the units of length, mass and time are respectively metre, kilogram and second.
CGS System : The full form of CGS system is Centimetre Gram Second. CGS system is also known as Gaussian system. In CGS system, the units of length, mass and time are respectively centimetre, gram and second.
FPS System : The full form of FPS System is Foot Pound Second. FPS is also known as British system. In FPS system, the units of length, mass and time are respectively foot, pound and second.
SI System : SI system is generally known as International System of Units. It is the modification form of MKS system. SI System of unit is adopted to have same common unit world-wide.
Macro and Micro Prefixes
Micro- is a prefix used to describe something that is small scale, while macro- is a prefix used to describe something that is large scale.
|
Macro Prefix |
Symbol |
Value |
|---|---|---|
|
kilo |
k |
103 |
|
mega |
M |
106 |
|
giga |
G |
109 |
|
tera |
T |
1012 |
|
peta |
P |
1015 |
|
exa |
E |
1018 |
|
zetta |
Z |
1021 |
|
yotta |
Y |
1024 |
|
Micro Prefix |
Symbol |
Value |
|---|---|---|
|
centi |
c |
10-2 |
|
milli |
m |
10-3 |
|
micro |
μ |
10-6 |
|
nano |
n |
10-9 |
|
pico |
p |
10-12 |
|
femto |
f |
10-15 |
|
atto |
a |
10-18 |
|
zepto |
z |
10-21 |
|
yocto |
y |
10-24 |
Units of Length, Mass and Time
The different units used to represent length, mass and time are shown below in the table:
|
Units of Length |
Units of Mass |
Units of Time |
|---|---|---|
|
1 Angstrom = 10-10 m |
1 Quintal = 102 kg |
1 minute = 60 second |
|
1 Light year = 9.46 × 1015 m |
1 Metric tone = 103 kg |
1 Hour = 60 minute = 3600 second |
|
1 AU ( Astronomical Unit) = 1.5 × 1011 m |
1 Atomic mass unit = 1.66 × 10-27 kg |
1 Day = 24 hours = 1440 min = 86400 s |
|
1 Mile = 1.6 km |
1 Pound = 0.4537 kg |
1 Lunar month = 28 days |
|
1 Fermi = 10-15 m |
1 Slug = 14.59 kg |
1 Solar month = 30 or 31 days |
Important Formulas of Derived Units
Following table shows some of the examples of derived units from fundamental units.
|
Physical Quantity |
Formula |
SI Units |
|---|---|---|
|
Area of square |
(side)2 |
m2 |
|
1/2×Base×Height |
m2 |
|
|
Mass/Volume |
kg m-3 |
|
|
change in velocity/time |
ms-2 |
|
|
Force/Area |
Nm-2 or Pascal |
|
|
P/E = mgh |
N-m or joule |
|
|
Work/time |
Js-1 or watt |
|
|
Displacement/Time |
ms-1 |
|
|
Mass × Acceleration |
kg ms-2 or newton |
|
|
Mass × Velocity |
kg ms-1 |
|
|
Force/(Electric current × Displacement) |
N amp-1 m-1 or tesla or weber/m2 |
|
|
Force × Time |
N-s |
|
|
Length × Breadth × Height |
m3 |
Units and Dimensions
Units and Dimensions is a fundamental and essential topic in Physics. For the measurement of a physical quantity, Unit plays a vital role. Unit provides a complete idea about the measurement of a physical quantity. Dimension is a measure of the size or extent of a particular quantity.
In this article, we will learn Units and Dimensions related all details including definition, fundamental and derived units, system of units, List of Units of physical quantities, Dimension formula, List of physical quantities and their dimensions, etc.
Table of Content
- What are Units?
- Fundamental and Derived Units
- What are Dimensions?
- Dimensional Formula
- Dimensionless Quantities