1
Chapter 1: Introduction to Physics
1.1 Understanding Physics
explain what physics is
recognize the physics in everyday objects and natural phenomena 1. A phenomenon is an occurrence that can be perceived by our senses.
2. In physics, we study natural phenomena, such as the eruption of volcano, rain fall, formation of rainbow and the properties of matter , such as length, temperature, volume
3. There are many fields of study in physics, including force, motion, heat, light, waves, electricity, electromagnetism, electronics and nuclear physics. 1.2
Understanding Base Quantities and Derived Quantities
explain what base quantities and derived quantities are
list base quantities and their units
list some derived quantities and their units.
express quantities using prefixes.
express quantities using scientific notation
express derived quantities as well as their units in terms of base quantities and base units.
solve problems involving conversion of units 1.
A physical quantity is a physical characteristic that can be measured.
2.
Base quantities are physical quantities that cannot be defined in terms of other base quantities.
There are five base quantities: length, mass, time, current and temperature.
Physical Quantity Base S.I. Unit Base Quantity Quantity Symbol S.I. Unit Unit symbol Length
l
m
etre
m
Mass
m
kilogram
kg
Time
t
second
s
Electric Current
I
ampere
A
Temperature
T
kelvin
K
Table 1
Notes for teachers:
Symbol is a short form of a quantity. Example: A boy by the name Ahmad is called as “Mad”; a girl by
the
name Mary Jane is called “MJ”; a pet by the name
cute
cute is called “cc”.
Unit is similar to the penjodoh bilangan in the Bahasa Melayu.
For person, we say “seorang” or “dua orang”; but for a pet like hamsters, we say “seekor” or “dua ekor”.
The unit ampere and kelvin are the names of scientists we use to remind us of their contributions to the respective fields. However, when we write the unit fully, we write all in small letters, example: 1.2 ampere, 5.0 kelvin; when we write shortly, we write the first alphabet of the name in capital letter, example: 1.2 A, 5.0 K
3. Derived quantities are physical quantities consisting of combinations of base quantities., by
multiplication, division, or both operations. 4.
Derived quantities as well as their units are expressed in terms of base quantities and base S.I. units as follows:
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Notes for teachers: Example: Given that velocity =
timent displaceme
. Express the unit for speed in base units. Solution: SI unit for velocity =
for timeunit SIntdisplacemefor unit SI
=
sm
= ms
1
(read as metre per second)
Given that
l
: length,
m
: mass,
t
: time,
I
: electric current,
T
: temperature. Derived quantities (symbol) Expressed in base quantities Derived units
Area (A)
A = l x l
Unit A = m x m =
2
m
(read as square metre)
Volume (V)
V = l x l x l
Unit V = m x m x m =
3
m
(read as cubic metre)
Density (
ρ
)
Ρ =
V m
Unit ρ =
3
mkg
=
3
mkg
(read as kilogram per cubic metre)
Speed (v)
v =
t l
Unit v =
sm
=
1
sm
(read as metre per second)
Work or Energy (W or E)
W = F
s F = force s = displacement
Unit W = kg
2
sm
x m = kg
22
sm
= N m = J (read as joule)
Power (P) P =
t E t W
Unit P =
s J
=
1
s J
= W (read as watt)
Velocity (v) v =
t l
Unit v =
sm
=
1
sm
(read as metre per second)
Acceleration (a) a =
tu
v
u = initial velocity v = final velocity t = time taken
Unit a =
sms
1
=
2
sm
(read as metre per second per second)
3
Force (F) F = ma m = mass a = acceleration
Unit F = kg x
2
sm
= kg
2
sm
= N (read as newton)
Impulse (Ft) Ft = change of momentum = mv
–
mu m = mass u = initial velocity v = final velocity
Unit Ft = kg x
1
sm
= kg
1
sm
= N s (read as newton second)
Momentum (p) p = mv m = mass v = velocity
Unit p = kg x
1
ms
= kg
1
sm
= N s (read as newton second)
Pressure (P) P =
A F
F = force A = area
Unit P =
2
m N
=
2
m N
= Pa (read as pascal)
Specific heat capacity (c) c =
mQ
Q = heat energy m = mass
= change in temperature
Unit c =
C kg J
o
=
101
C kg J
=
kgK J
=
11
K kg J
(read as joule per kilogram per kelvin)
Frequency (f) f =
T
1
T = period of swing; unit: second (s)
Unit f =
s
1
=
1
s
= Hz (read as hertz)
Electrical charges (Q) Q =
It
I = electric current t = time
Unit Q = A s = C (read as coulomb)
Resistance (R) R =
I V
V = voltage; unit: volt (V) I = electric current
Unit R =
AV
=
1
AV
=
(read as ohm) Table 2
4 5. Prefixes are used to express some physical quantities that are either very big or very small. Prefix Symbol Value Tera
T
12
10
Giga
G
9
10
Mega
M
6
10
kilo
k
3
10
desi
d
1
10
centi
c
2
10
mili
m
3
10
mikro
6
10
nano
n
9
10
piko
p
12
10
Table 3 6. Standard form or scientific notation: A x 10
n
where 1
A
10, n is an integer (integer positive or negative). Physical Quantity Value Standard form or Scientific notation Mass of earth 6 020 000 000 000 000 000 000 000 kg
kg
24
1002.6
Diameter of an oil molecule 0. 000 000 000 74 m
m
10
104.7
Speed or light in the vacuum 299 792 458 m s

18
100.3
sm
Radius of earth 6 370 000 m
m
6
1037.6
Mass of hydrogen atom 0. 000 021 kg
kg
5
101.2
Time of a day 86 400 s
s
4
1064.8
Temperature of the centre of the earth 6 000 000 K
K
6
100.6
Size of a flu virus 0.000 000 2 m
m
7
100.2
Table 4