2. Specific Instructional
Objectives
At the end of the lesson, you should be able to:
 show understanding that all physical quantities consists of a numerical magnitude
and a unit.
 Recall the following base quantities and their units mass (kg), length (m), time (s),
current (A), temperature (K) amount of substance (mol)
 use the following prefixes and their symbols to indicate decimal sub-multiples and
multiples of the SI units: nano (n), micro (μ), milli (m), centi (c), deci (d), kilo (k),
mega (M)
 show an understanding of the orders of magnitude of the sizes of common objects
ranging from a typical atom to the Earth
 state what is meant by scalar and vector quantities and give common examples of
each
 add two vectors to determine a resultant by a graphical method
 describe how to measure a variety of lengths with appropriate accuracy by means
of tapes, rules, micrometers and calipers, using a vernier scale as necessary
 describe how to measure a short interval of time including the period of a simple
pendulum with appropriate accuracy using stopwatches or appropriate instruments

3. Unit 1: Physical
Quantities and Units

4. Specific Instructional
Objectives
At the end of the lesson, you should be able to:
1. show understanding that all physical quantities
consists of a numerical magnitude and a unit.
2. Recall the following base quantities and their
units mass (kg), length (m), time (s), current
(A), temperature (K), amount of substance
(mol)

5. 1.1 Physical Quantities
Quantitative vs Qualitative
(Measurements vs Descriptions)
•Scientists do not use descriptions to make
observations as these would most likely
cause disagreements.
•“How large is large?” or “How small is
small?”
•Instead, sizes are specified using a number
and a standard unit such as the metre.

6. What is a Physical Quantity???
Definition:
 A physical quantity is one that can be
measured and that consist of a numerical
magnitude and a unit.
 Examples include length, volume, time
and temperature.
What other
physical
quantities can
you think of?

7. Magnitude and Unit
 All
physical quantities consists of a numerical
magnitude (size) and a unit.
E.g. My height = 1.76 m
E.g. The temperature today is 29 oC

8. Base Quantity
 There are 7 base quantities.
 All the other quantities (derived quantities)
can be worked out from the 7 base quantities.
Base Quantities
Why are these
1. Length
quantities called
2. Mass base quantities?
3. Time
4. Temperature
5. Electric current
6. Luminous intensity
7. Amount of substance

9. SI units
 French ‘Le Systeme International d’ Unites’
 English translation: ‘International System of
units’
 This set of units is internationally
accepted/agreed by scientist
 Imperial Units versus Metric Units

10. 7 Base Quantities and their SI Units
Base Quantities SI units
1. Length (l) metre (m)
2. Mass (m) kilogram (kg)
3. Time (t) second (s)
4. Temperature (T) kelvin (K)
5. Electric current (I) ampere (A)
6. Luminous intensity (Iv) candela (cd)
7. Amount of substance mole (mol)
(n)
http://physics.nist.gov/cuu/Units/index.html

11. SI Units of derived quantities
Example
(a) Area = length × breadth
m m
∴SI unit of area = m × m = m 2
mass kg
(b) density =
volume m3
∴SI unit of density = kg/m 3 (or kgm -3 )

12. 1.2 SI Units
Derived Quantities
Derived quantities Symbol for unit Special name
area m2
volume m3
density kg m−3
speed m s—1
acceleration m s—2
force kg m s—2 (N) newton (N)
pressure kg m−1 s−2(N m−2) pascal (Pa)
work kg m2 s−2 (N m) joule (J)
power Kg m2 s−3 (J s−1) watt (W)

13. Quick Check
1. Name the base quantities and identify their
SI units.

14. Theory Workbook
Exercise 1.1 (page 1)
Q1 and Q2

15. Specific Instructional
Objectives
At the end of the lesson, you should be able to:
1. use the following prefixes and their symbols to
indicate decimal sub-multiples and multiples of
the SI units: nano (n), micro (μ), milli (m), centi
(c), deci (d), kilo (k), mega (M)
2. show an understanding of the orders of
magnitude of the sizes of common objects
ranging from a typical atom to the Earth

16. Understanding prefixes
kilogram
prefix
kilo = 103 = 1000
Therefore 1 kilogram = 1000 gram
1 km = ________m 1 kJ = ________J

17. Understanding prefixes
centimetre
prefix
centi = 10-2 = 0.01
Therefore 1 centimetre = 0.01 metre

18. Common Prefixes
Factor Name
109 Giga (G)
106 mega (M)
103 kilo (k)
10-1 deci (d)
10-2 centi (c)
10-3 milli (m)
10-6 micro (µ)
10-9 nano (n)

19. Why do we need
Example prefixes?
Write
(a) 50 megawatts (MW) in watts (W)
(b) 250 nanoseconds (ns) in seconds (s)
(a ) 50 MW = 50 × 10 6 W
= 50000000 W
−9
(b) 250ns = 250 × 10 s
= 0.00000025 s

20. Approximate length of some
objects
Distance from Earth to Sun 1.5 x 1011 m
Radius of the Earth 6 x 106 m
Height of Mount Everest 1 x 104 m
Length of a football field 1 x 102 m
height of a 4 year-old child 1m
length of a bee 6 x 10-3 m
diameter of a strand of hair 1 x 10-4 m
diameter of a hydrogen 6 x 10-10 m
atom

21. Quick Check
1. Rewrite the following quantities using
suitable prefixes.
(a) 5 000 000 J 5 MJ
(b) 48 000 g 48 kg
(c) 0.0009 s 900 µs or 0.9 ms

22. Theory Workbook
Exercise 1.1 (page 1)
Q3

23. The Standard Form
Many measurements in modern scientific
fields involve very large and very small
numbers.
E.g.
Speed of light = 300 000 000 m/s
wavelength of violet light = 0.00000038 m
It is troublesome to write many zeroes for
very large and very small numbers.

24. The Standard Form
Hence mathematicians/scientists decided to use a
more convenient known as the standard form: E.g
3 00 000 000 can be written as
3.0 × 100 000 000
= 3.0 × 108 m/s (standard form)
The standard form is always written as
A × 10n,
Where 1 < A < 10 and n is an integer

25. Which of these figures in standard form?
0.5 × 106 1.002 × 105
2.6 × 103
105 × 108
9.9 × 10-8

26. The Standard Form
Example: Express the following as standard
form:
(i)
4.0 0 0 0 0
= 4.0 × 105
(ii) 3 .4 5 0 0 0 0
= 3.45 × 106

27. The Standard Form
Example: Express the following as standard
form:
(i)
2.2 2 0
= 2.22 × 103
(ii) 1 .0 1
= 1.01 × 102

28. The Standard Form
Very small numbers can also be written as
standard form: For example
0.038 can be written as
3.8 × 10-2
A × 10n

29. The Standard Form
Example: Express the following as standard
form:
(i)
0. 0 0 0 0 1. 2 5
= 1.25 × 10-5
(ii) 0. 0 0 0 3 . 4
= 3.4 × 10-4

30. The Standard Form
Example: Express the following as standard
form:
(i)
0. 0 0 0 0 0 2. 2 3
= 2.23 × 10-6
(ii) 0. 0 1.
= 1.0 × 10-2

31. The Standard Form
Example: Express the following in ordinary
notation:
(a) 1.25 × 103
(b) 4.3 × 106
(c) 2.6 × 10-3
(d) 8.7 × 10-5

32. Theory Workbook
Exercise 1.1 (page 1)
Q4

33. Prefix and standard form
50,000,000 W
= 50MW (prefix)
= 5 x 107 W (standard form)
Both prefixes and
use of standard form
reduces the need to
write many zeros.
Which is better?

34. Specific Instructional
Objectives
At the end of the lesson, you should be able to:
1. describe how to measure a variety of lengths
with appropriate accuracy by means of tapes,
rules, micrometers and calipers, using a
vernier scale as necessary.

35. Measurement of lengths
Which instrument would you use to measure
the length of a pencil?
A 15-cm or 30-cm rule

36. Measurement of lengths
Which instrument would you use to measure
the length of your desk?
A metre rule

37. Measurement of lengths
Which instrument would you use to measure
the length of a room?
A measuring tape

38. Measurement of lengths
Which instrument would you use to measure
the length of a school field?

39. Measurement of lengths
Which instrument(s) would you use to measure
the thickness of a pencil?
0.922 cm
0.9 cm 0.92 cm
Micrometer
ruler Vernier calipers screw
gauge

40. Measurement of Length
Measuring Instrument Range Precision
Measuring tape 0–5m 0.1 cm
Metre rule 0–1m 0.1 cm
Vernier calipers 0 – 15 cm 0.01 cm
Micrometer 0 – 2.5 cm 0.001 cm
screw gauge

41. Quick Check
Which instruments would you use to measure the lengths
of the following?
Diameter of a Internal diameter Length of your
strand of hair of a mug textbook

42. Vernier Calipers

43. Vernier Calipers
mm
23 6
Measured value is
between 23 and 24 mm
6
= 23. __ mm

44. Vernier Calipers
2.9_ cm
4
Vernier scale
0 5 10
0 cm 3 cm 4 cm
Main scale

45. Theory Workbook
Exercise 1.3 (page 3)
Q4
(a) 3.43 cm
(b) 1.39 cm

46. Parts of a vernier calipers
inner jaws
Depth bar
Outer jaws

47. 1.5 Measurement of Length and Time
Accurate Measurement
• Two main types of errors
Random errors Systematic errors
Random errors because they Not random but constant
are unpredictable
They arise when observers Due to the equipment being
estimate the last figure of a used – e.g. a ruler with zero
reading on an instrument. error
Minimized by averaging a Cannot be reduced by
large number of readings averaging, but they can be
eliminated if the sources of
the errors are known

48. Zero Error on a Vernier Scale
What is
Zero Error???
Definition:
If the zero marks on the main scale and vernier scale
do not coincide when the jaws are closed, there is a
zero error.

49. Zero Error Subtracted from Reading
4th line after zero on
vernier scale coincides
with line on main
scale: zero error = 0.04
cm
Zero error is subtracted from the reading

50. Zero Error Added to Reading
7th line after zero on vernier scale
coincides with line on main scale:
Zero error = 0.1 – 0.07
= 0.03 cm

51. Zero Error Added to Reading
0.07 cm

52. Zero Error Added to Reading
7th line after zero on vernier scale
coincides with line on main scale:
Zero error = 0.1 – 0.07
= 0.03 cm Zero error is ‘added’ to the reading
Note: By convention, ‘under-read’ zero error is negative, i.e.
the zero error in this case is – 0.03 cm.

53. Textbook
 Read TB pg 13

54. Example
Zero error
Reading
= +0.08 cm
when jaws
are closed
Reading on scale
= 0.64 cm
Reading when jaws Thickness of coin
are used to measure = 0.64 – 0.08
the thickness of a
coin = 0.56 cm

55. Example
0 5 10
Zero error
0 1
cm
= - 0.02 cm
Reading when jaws are closed
0 5 10
Reading on scale
= 0.84 cm
1 cm 2 cm
Thickness of coin
= 0.84 – (- 0.02)
Reading when jaws are used to measure
the thickness of a coin = 0.86 cm

56. The micrometer screw gauge
http://members.shaw.ca/ron.blond/Micrometer.APPLET/

57. The micrometer screw gauge
0.14 mm
mm
5.5 mm
Reading
= main scale R + thimble scale R
= 5.5 + 0.14 = 5.64 mm

58. The micrometer screw gauge
mm
5.14 mm

59. The micrometer screw gauge
35
30
mm
25
7.29 mm

60. The micrometer screw gauge
35
30
25
3.79 mm

61. The micrometer screw gauge
45
40
35
4.39 mm

62. The micrometer screw gauge
45
40
35
6.89 mm

63. Theory Workbook
Exercise 1.3 (page 3)
Q5
(a) 4.13 mm
(b) 2.79 mm

64. Precautions when using a
micrometer
 Avoid over-tightening  use the ratchet for
fine adjustment
 Clean the ends of anvil and spindle before
measuring.
 Check for zero-error (read TB page 14)

65. Zero-error

66. Theory Workbook
Exercise 1.3 (page 3)
Q6
Zero error = -0.02 mm
Reading on scale = 1.19 mm
Thickness of the coin = 1.19 – (-0.02)
= 1.21 mm

67. Specific Instructional
Objectives
At the end of the lesson, you should be able to:
1. describe how to measure a short interval of
time including the period of a simple
pendulum with appropriate accuracy using
stopwatches or appropriate instruments

68. How to measure time?

69. http://www.phy.ntnu.edu.tw/oldjava/pendulum30/pendulum.html
A simple pendulum
Pendulum.mht http://www.fearofphysics.com/Pendulums/pendhl.html
1 oscillation
=A–O–B–O–A
Or: 1 oscillation
=O–B–O–A-O
The Period (T) of a
pendulum is the
time taken for 1
complete
oscillation. A B
O

70. Pendulum Lab

71. Stop Watches
Human Reaction Time: 0.3 s

72. Theory Workbook
Exercise 1.3 (page 3-4)
Q1
Q9
Q10
Q11
1 (a) Metre rule; (b) vernier calipers; (c) micrometer screw
gauge; (d) zero error; (e) period
9 28.4 s; 2 min 25.6 s; 2 min 55.6 s
10 34.26 s; 1 min 23.48 s
11 (a) 0.64 s; (b) 0.16 s; (c) The period of oscillatoin
increases

73. Ticker-Tape Timer
Frequency:
50 dots per
second
1
S
50

75. Class Practice/ Homework
Self-Management (TB page 23)
Misconception Analysis
 Q1 – 10
Practice (TB page 23 – 25)
Q3 and 4
Q1 on unit conversion is a bit challenging
(optional)