Topics covered in this snacksized chapter:
Measurement is the process or the result of determining the ratio of a physical quantity, such as a length, time, temperature etc., to a unit of measurement, such as meter, second or degree Celsius.
The science of measurement is called metrology.
Measurement is collection of quantitative data.
A measurement is made by comparing a quantity with a standard unit.
Physics is a mathematical science.
The metric system is the system of measurement used by scientists to express mass, length, and volume.
In an effort to standardize terms for the measurement of energy, force, work, and power, scientists have developed a common system of terminology called System International (SI) units
Scalars are quantities that are fully described by a magnitude (or numerical value) alone.
Examples of scalar quantities are time, volume, mass, temperature etc.
Vectors are quantities that are fully described by both a magnitude and a direction.
A vector of dimension n is an ordered collection of n elements, which are called components.
Examples of vector quantities are distance, velocity, etc.
Quantities like force, acceleration, velocity all needs to specify direction so they are vector quantities.
The International System of Units^{
}is the modern form of the metric system.
It comprises a system of units of measurement devised around seven base units and the convenience of the number ten.
The International System of Units (SI) defines seven units of measure as a basic set from which all other SI units are derived.
These SI base units and their physical quantities are
Base Quantity
 Name
 Symbol

Length
 meter
 M

Mass
 kilogram
 Kg

Time
 second
 S

Electric Current
 ampere
 A

Thermodynamic Temperature
 kelvin
 K

Amount of Substance
 mole
 Mole

Luminous Intensity
 candela
 Cd

The International System of Units (SI) specifies a set of seven base units from which all other units of measurement are formed, by products of the powers of base units. These other units are called SI derived units.
Derived Quantity
 Name
 Symbol

Area
 square meter
 m^{2
}

Volume
 cubic meter
 m^{3
}

Speed
 meter per second
 m/s

Velocity
 meter per second
 m/s

Acceleration
 meter per second squared
 m/s^{2
}

Wavenumber
 reciprocal meter
 1/M

Density, Mass Density
 kilogram per cubic meter
 kg/m^{3
}

Specific Volume
 cubic meter per kilogram
 m^{3
}/kg

Current Density
 ampere per square meter
 A/m^{2
}

Energy
 Joule
 Kg m^{2
}/s^{2
}

Force
 Newton
 Kg m/s^{2
}

Wavenumber
 reciprocal meter
 1/M
