Physical quantitiesPhysical quantities are are quantities that can be quantities that can be measuredmeasured..

A physical quantities can be A physical quantities can be represented by :represented by :

symbolsymbol of the quantityof the quantity

a numerical value for the a numerical value for the magnitudemagnitude of the quantity of the quantity

the the unit unit of measurementof measurement

For example,For example,

Height of the girl, Height of the girl, l = l = 1.55 m1.55 m

Symbol of the physical

quantity

Numerical value for the magnitude of the physical

quantity

Unit of the physical quantity

Base quantities are physical quantities that cannot be defined in terms of other base quantities

Base Base quantityquantity

SymbolSymbol SI unitSI unit Symbol of Symbol of SI unitSI unit

LengthLength ll metremetre mm

MassMass mm kilogramkilogram kgkg

TimeTime tt secondsecond ss

TemperatureTemperature TT KelvinKelvin KK

Electric Electric

currentcurrent

II ampereampere AA

Derived quantity Derived quantity is is obtained by combining obtained by combining base quantities by base quantities by multiplication or division multiplication or division or both these operations.or both these operations.

Example:Example:

1( ), :

( )

length mVelocity unit ms

time s

2( ) ( ), :Area length m xlength m unit m

3

( )

( ) ( ) ( )

, :

mass kgDensity

length m xlength m xlength m

unit kgm

Standard formStandard form powers of the base number 10powers of the base number 10

A x 10A x 10nn

and A can be an integer and A can be an integer or decimal number.or decimal number.n is a positive integer for a number n is a positive integer for a number greater than one or negative integer greater than one or negative integer for a number less than one for a number less than one

101 A

Example:Example:70.0000002 2 10m x m

61276000 1.27 10m x m

Are used to Are used to simplifysimplify the description of the description of physical quantities physical quantities that are either that are either very very bigbig or or very smallvery small..

Prefix Prefix SymbolSymbol ValueValue

PicoPico pp 1010-12-12

NanoNano nn 1010-9-9

MicroMicro 1010-6-6

MiliMili mm 1010-3-3

CentiCenti cc 1010-2-2

DeciDeci dd 1010-1-1

KiloKilo kk 101033

MegaMega MM 101066

GigaGiga GG 101099

TeraTera TT 10101212

•A scalar quantity is quantity which has only magnitude or size

•A vector quantity has both magnitude and direction

Scalar quantityScalar quantity Vector Vector QuantityQuantity

LengthLength TimeTime DisplacementDisplacement

SpeedSpeed TemperatureTemperature VelocityVelocity

MassMass DensityDensity AccelerationAcceleration

AreaArea VolumeVolume MomentumMomentum

WorkWork EnergyEnergy ForceForce

EXAMPLEEXAMPLE

►The maximum speed for a The maximum speed for a car in Malaysian highways is car in Malaysian highways is 110 km h110 km h-1-1

►What is this value in m sWhat is this value in m s-1-1??

A measuring tape is used to measure lengths A measuring tape is used to measure lengths of several metres. Its accuracy is up to 0.01mof several metres. Its accuracy is up to 0.01m

A metre rule is used to measure lengths of a A metre rule is used to measure lengths of a few centimetres to a metre. Its accuracy is up few centimetres to a metre. Its accuracy is up to 0.1mto 0.1m

A vernier callipers is used to measure lengths A vernier callipers is used to measure lengths of less than 10 cm. It is also suitable for of less than 10 cm. It is also suitable for measuring internal or external diameter of measuring internal or external diameter of round objects. Its accuracy is up to 0.01 cmround objects. Its accuracy is up to 0.01 cm

A micrometer screw gauge is used for A micrometer screw gauge is used for measuring very small objects. Its accuracy is measuring very small objects. Its accuracy is up to 0.01 mm.up to 0.01 mm.