# Measurements

## Classification of physical quantities

1. Fundamental quantities - Not derived from other quantities.
E.g. length, mass and time.
2. Derived quantities - Derived from fundamental quantities.
E.g. velocity, area and acceleration.
3. Scalar quantities - Have magnitude, Not direction.
E.g. velocity, work and power.
4. Vector quantities - Have both magnitude and direction.
E.g. force, velocity and acceleration.

Unit is the standard measure of a quantity. There are 7 basic units.
E.g. time, length, mass, electric current, thermodynamic temperature, amount of substance, luminous intensity.
Qunatity SI Unit
Acceleration Metre/second square (m/s2)
Amount of substance Mole (mol)
Area Square Metre (m2)
Electric charge Coulomb (C)
Electric current Ampere (A)
Electric potential Volt (V)
Energy Joule (J)
Frequency Hertz (Hz)
Force Newton (N)
Impulse NewtonSecond (Ns)
Inductance Henry (H)
Length Metre (m)
Luminous intensity Candela (cd)
Magnetic field Tesla (tesla)
Magnetic flux Weber (Wb)
Mass Kilogram (kg)
Moment of inertia Kilogram square meter (Kgm2)
Momentum KilogramMeter/second (Kgm/s)
Power Watt (W)
Pressure Pascal (Pa)
Resistance Ohm (Ω)
Time Second (s)
Temperature Kelvin (K)
Velocity Metre/second (m/s)
Volume Cubic metre (m3)
Work Joule (J)

## Metric system

Ptefix Symbol Multiplier
deca da 101
hecto h 102
kilo k 103
mega M 106
giga G 109
tera T 1012
peta P 1015
exa E 1018
zetta Z 1021
yotta Y 1024
deci d 10-1
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