PHYSICAL QUANTITY

1. CHAPTER 1:
Physical Quantities &
Measurements
Physical quantities & units
Noor Azie Azura Mohd Arif
Physics Division
Centre for Pre-University Studies
Universiti Malaysia Sarawak

2. Learning Outcome
At the end of this chapter students should be able to:
State the basic quantities and their respective S.I
units and symbols.
State the derived quantities and their respective
units and symbols.
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3. Physical Quantity
A quantity that can be measured using standard size called
unit.
Example: length, mass, time and etc
Every physical quantity consists of a numerical magnitude and
a unit.
Example: Length of wire = 50.0 cm
Physical quantity can be classified as a basic quantity and
derived quantity.
Physical
Quantity
Numerical
Value
Unit
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4. Base Quantities
Quantities that are in the simple form and cannot be defined
in terms of other physical quantities.
There are seven basic quantities.
Base Quantity Quantity Symbol Symbol Unit Symbol
Length l, x, y, r etc Metre m
Mass m Kilogram kg
Time t Second s
Electric current I Ampere A
Temperature T Kelvin K
Quantity of matter n Mole mol
Luminous intensity L Candela cd
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5. Derived Quantities
Quantities that are obtained from the combination of various
base quantities.
They are derived from the base quantities through
multiplication, division or both.
Derived Quantities Relationship SI derived unit
Area Length × Width m2
Velocity Displacement/ time ms-1
Acceleration Velocity / time ms-2
Force Mass × acceleration kg m s-2
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6. SI Prefixes
A conversion factor for converting one unit to another unit.
To avoid writing too many zeroes which give rise to human error.
Prefix Symbol Multiplying Factor
Tera T 1012
Giga G 109
Mega M 106
Kilo k 103
Deci d 10-1
Centi c 10-2
Milli m 10-3
Micro µ 10-6
Nano n 10-9
Pico p 10-12
Tengkorak
Gorila
Merah
Kerana
Dia
Suka
Makan
Makanan
Nasi
Pedas
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7. Express the following quantities in SI units:
Area = 50 mm2
Volume = 20 cm3
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Express the density of water = 1.0 g cm-3 in SI units
TRY !!!
(Ans: 1000 kg m-3)
TRY !!!

8. 8
Physical Quantities
Base and derived quantities
SI Prefixes
Physical Quantity
(Quantity that can be measured using standard size
called the unit)
Base Quantity
(Quantity which is not a
combination of other
physical quantities)
Example: length, mass,
time, electric current,
temperature, quantity of
matter, and luminous
intensity
Derived Quantity
(Quantity which is a
combination of two or more
physical quantities)
Example: area, density,
velocity, force
SI Prefixes:
 A conversion factor for converting one unit to another
unit.
 To avoid writing too many zeroes which give rise to
human error.
SUMMARY