MechanicsMeasurement

A physical quantity is a quantity that can be measured.

Examples of physical quantities are a) Lengthb) Mass c) Temperatured) Time and e) Energy .

Every physical quantity has a numerical size and a unit. All units must be written, even in intermediate working. Example: 15 m + 12 m = 27 m. (Not: 15 + 12 = 27 m)

MechanicsMeasurementSI UnitsScientists around the world agree to use the SI units for measuring physical quantities.

The SI units for all other physical quantities can be expressed in terms of these base quantities.

Fundamental Quantity

SI Unit Symbol

Length Metre mMass Kilogram kgTime Second sTemperature Kelvin K

MechanicsMeasurementExamples:Volume of a cube = length x length x lengthHence, SI unit of volume = SI unit of length x SI unit of length x SI unit of length = m x m x m = m3. Density = Mass / VolumeHence, SI unit of density = SI unit for mass / SI unit for volume = kg m3

MechanicsMeasurement

MechanicsMeasurement