Chapter 1 PHYSICAL QUANTITIES AND MEASUREMENT

CHAPTER

1

CHAPTER 1

PHYSICAL QUANTITIES AND
MEASUREMENT

1

ENGINEERING SCIENCE FOR POLYTECHNIC STUDENTS
CHAPTER 1:

PHYSICAL QUANTITIES AND MEASUREMENT

SUMMARY OF THE CHAPTER

1.1 Physical quantities
1.1.1 Scalar and vector Quantities
1.1.2 Base quantities, derived quantities and International System (SI) of units

1.2 Measurement and errors in measurement
1.2.1 Consistency, accuracy and sensitivity
1.2.2 Random error and systematic error

1.3 Unit Conversion
1.3.1 Convert Metric Units and Customary Units

1.4 Readings of measurement tools
1.4.1 Vernier calipers
1.4.2 Micrometer screw gauge

2 Chapter 1 : Physical Quantities and Measurement

2020 EDITION

CONCEPTUAL MAP

PHYSICAL QUANTITIES
AND MEASUREMENT

INTRODUCTION

PHYSICAL MEASUREMENT
QUANTITIES

Base Vector Tool of Error
quantities quantities measurement

Derived Scalar Systematic Random
quantities quantities error error

Vernier Zero Parallax
Calipers Error Error

Prefixes Micrometer
Screw Gauge
Scientific notation
(Standard form)

Unit Conversion

3

ENGINEERING SCIENCE FOR POLYTECHNIC STUDENTS

1.1 PHYSICAL QUANTITIES

• Physical quantity is the quantity that can be measured.

• Examples of physical quantities are the room temperature, the volume of a block
of wood, the speed of a car, the pressure of a gas, the weight of a person, etc.

• A physical quantity consists of two parts, a numerical value, and a unit of
measurement. For example,

Mass, m of a girl = 54 kg

Physical quantity and Numerical Unit of
symbol value measurement

Figure 1.1: Example of physical quantity

• Physical quantities are categorized into base quantities and derived
quantities.

• Unit of measurement used is the International System of Units (SI units).

1.1.1 Base quantities, derived quantities, and International System (SI) of units.

• Base quantities
- Base Quantities are physical quantities that cannot be defined in term of
other physical quantities.

Table 1.1: Base quantities and their respective SI units

Base Quantities Symbol SI Unit
• Length ( )
• Mass ( )
• Time ( )

• Temperature @ ( )

• Electric current ( )

4 Chapter 1 : Physical Quantities and Measurement

















2020 EDITION

1.3 UNIT CONVERSION

1.3.1 Convert Metric Units and Customary Units

• Metric Units
- The metric units of measurements are used anywhere outside of the United States-

elsewhere in the world.
- Metric is a based on the powers of 10.

• Customary Units
- Commonly known as English units or standard units.
- Customary units of measure are the units of measure that are used only in the

United States.

Table 1.6: Measurement Chart

LENGTH Customary

Metric 1 mile = 1760 yards
1 mile =5280 feet
1 kilometre = 1000 metres 1 yard = 3 feet
1 metre = 100 centimetres 1 foot = 12 inches
1 centimetre =10 millimetres

CAPACITY AND VOLUME

Metric Customary

1 liter = 1000 milliliters 1 gallon = 4 quarts
1 gallon = 128 ounces
1 quart = 2 pints
1 pint = 2 cups
1 cup = 8 ounces

MASS AND WEIGHT

Metric Customary

1 kilogram = 1000 grams 1 ton = 2000 pounds
1 gram = 1000 milligrams 1 pound = 16 ounces

1 year TIME 1 day = 24 hours
1 year 1 hours = 60 minutes
1 year = 365 days 1 minute = 60 seconds
1 week = 12 months
= 52 weeks
= 7 days

13

ENGINEERING SCIENCE FOR POLYTECHNIC STUDENTS

Table 1.7: Converting between measurement systems

Customary to Metric Conversion

Length Weight/Mass Capacity
1 fluid ounce ≈ 29.6 milliliters
1 inch = 2.54 centimeters 1 ounce ≈ 28.3 grams 1 quart ≈ 0.946 liter
1 gallon ≈ 3.79 liters
1 foot ≈ 0.305 metre 1 pound ≈ 0.454 kilogram

1 yard ≈ 0.914 metre

1 mile ≈ 1.61 kilometres

Metric to Customary Conversion

Length Weight/Mass Capacity
1 centimetre ≈ 0.39 inch 1 gram ≈ 0.035 ounce 1 milliliter ≈ 0.034 fluid ounce
1 metre ≈ 3.28 feet 1 kilogram ≈ 2.20 pounds 1 liter ≈ 1.06 quarts
1 metre ≈ 1.09 yards 1 liter ≈ 0.264 gallon
1 kilometre ≈ 0.621 mile

Worked Example 2
A wooden stick is 29 ℎ ( ). How long is the stick in ( )?

Solution: Therefore,
1 ℎ = 2.54 29 ℎ = 29 × 2.54
= 73.66

Worked Example 3
The weight of a sack of potatoes is 27 . How much would the sack of potatoes weight in
.

Solution: Therefore,
1 = 2.2

27 = 27 × 2.2
1 1

= 59.4

14 Chapter 1 : Physical Quantities and Measurement

2020 EDITION

Worked Example 4
Convert 3 ( ) to ℎ( )

Solution: Therefore,
1 = 100
3 = 3 × 100 × 1 ℎ
1 ℎ = 2.54 1 1 2.54

= 118 ℎ

Worked Example 5
Convert 24 to

Solution: Therefore,
1 = 4

24 = 24 × 1
1 4

= 6

Worked Example 6
Convert 3 ( ) to ( )

Solution: Therefore,
1 = 12 ℎ
1 ℎ = 2.54 3 = 3 × 12 × 2.54
1 1 1

= 91.44

15



















EXERCISE 2 2020 EDITION

1. What the reading for the following calipers in ? (5.64 )
a) (6.28 )
(0.02 )
Figure 1.16 (4.27 )

b) 25

Figure 1.17
c)

Figure 1.18
d)

Figure 1.19