2 Base And Derived Quantities

3. Physical quantitiesPhysical quantities are quantities are quantities
that can be 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

4. 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

5. Base quantities are physical quantities
that cannot be defined in terms of other
base quantities
KKelvinTTemperature
AampereIElectric
current
ssecondtTime
kgkilogrammMass
mmetrelLength
Symbol of
SI unit
SI unitSymbolBase
quantity

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

7. Example:Example:
1( )
, :
()
lengthm
Velocity unit ms
times
-
=
2
( ) ( ), :Area lengthmxlengthm unit m=
3
( )
( ) ( ) ( )
, :
masskg
Density
lengthm xlengthm xlengthm
unit kgm
-
=

8. Standard formStandard form
powers of the base number 10powers of the base number 10
A x 10A x 10
nn
and A can be an integer or and A can be an integer or
decimal number.decimal number.
n is a positive integer for a number n is a positive integer for a number
greater than one or negative integer for a greater than one or negative integer for a
number less than one number less than one
101<£A

9. Example:Example:
7
0.0000002 210m x m
-
=
6
1276000 1.2710m x m=

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

11. 10
9
GGiga
10
-12
pPico
10
12
TTera
10
6
MMega
10
3
kKilo
10
-1
dDeci
10
-2
cCenti
10
-3
mMili
10
-6
Micro
10
-9
nNano
Value Symbol Prefix
m

12. •A scalar quantity is
quantity which has only
magnitude or size
•A vector quantity has both
magnitude and direction

13. ForceEnergyWork
MomentumVolumeArea
AccelerationDensityMass
VelocityTemperatureSpeed
DisplacementTimeLength
Vector
Quantity
Scalar quantity

14. EXAMPLEEXAMPLE
►The maximum speed for a car The maximum speed for a car
in Malaysian highways is 110 in Malaysian highways is 110
km hkm h
-1-1
►What is this value in m sWhat is this value in m s
-1-1
??

15. A measuring tape is used to measure lengths of A measuring tape is used to measure lengths of
several metres. Its accuracy is up to 0.01mseveral metres. Its accuracy is up to 0.01m
A metre rule is used to measure lengths of a few A metre rule is used to measure lengths of a few
centimetres to a metre. Its accuracy is up to centimetres to a metre. Its accuracy is up to
0.1m0.1m
A vernier callipers is used to measure lengths of A vernier callipers is used to measure lengths of
less than 10 cm. It is also suitable for measuring less than 10 cm. It is also suitable for measuring
internal or external diameter of round objects. internal or external diameter of round objects.
Its accuracy is up to 0.01 cmIts accuracy is up to 0.01 cm
A micrometer screw gauge is used for measuring A micrometer screw gauge is used for measuring
very small objects. Its accuracy is up to 0.01 very small objects. Its accuracy is up to 0.01
mm.mm.