Science for Engineering

John Bird

• Publisher: Routledge
• Year: 2015
• Print ISBN: 9781138428997, 9781138428997
• eBook ISBN: 9781317575054
• Edition: 5
• Topic: Technology & Engineering
• Subtopic: Civil Engineering
• Index: Technology & Engineering

A practical introduction to the engineering science required for engineering study and practice.

Science for Engineering is an introductory textbook that assumes no prior background in engineering. This new edition covers the fundamental scientific knowledge that all trainee engineers must acquire in order to pass their exams, and has been brought fully in line with the compulsory science and mathematics units in the new engineering course specifications.

John Bird focuses upon engineering examples, enabling students to develop a sound understanding of engineering systems in terms of the basic laws and principles. This book includes over 580 worked examples, 1300 further problems, 425 multiple choice questions (with answers), and contains sections covering the mathematics that students will require within their engineering studies, mechanical applications, electrical applications and engineering systems.

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• Colour layout helps navigation and highlights key learning points, formulae and exercises

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• Understanding can be tested with the 580 worked examples, 1300 further problems and 425 multiple choice questions contained within the book

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• Focuses on real-world situations and examples in order to maximise relevance to the student reader

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This book is supported by a companion website of materials that can be found at www.routledge/cw/bird, this resource including fully worked solutions of all the further problems for students to access for the first time, and the full solutions and marking schemes for the revision tests found within the book for lecturers/instructors use. In addition, all 433 illustrations will be available for downloading by staff.

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Section II

Mechanical applications

Chapter 14

SI units and density

Why it is important to understand: SI units and density

In engineering there are many different quantities to get used to, and hence many units to become familiar with. For example, force is measured in newtons, electric current is measured in amperes and pressure is measured in pascals. Sometimes the units of these quantities are either very large or very small and hence prefixes are used. For example, 1,000,000 newtons may be written as 10⁶ N which is written as 1 MN in prefix form, the M being accepted as a symbol to represent 1,000,000 or 10⁶. Studying, or working, in an engineering discipline, you very quickly become familiar with the standard units of measurement, the prefixes used and engineering notation. An electronic calculator is extremely helpful with engineering notation. Knowledge about density inspired engineers to build ships, surfboards and buoys; density is also an important property that engineers consider in the engines they design for cars and power plants.

At the end of this chapter, you should be able to:

• state the seven SI units

• understand common prefixes used in engineering

• use engineering notation and prefix form with engineering units

• define density and relative density

• perform simple calculations involving density

14.1 SI units

As discussed in chapter 3, the system of units used in engineering and science is the Système Internationale d’Unités (International system of units), usually abbreviated to SI units, and which is based on the metric system. It was introduced in 1960 and is now adopted by the majority of countries as the official system of measurement.

The basic units in the SI system are listed below with their symbols:

Quantity	Unit	Symbol
Length	metre	m	(1m = 100cm = 1000mm)
Mass	kilogram	kg	(1kg = 1000g)
Time	second	s
Electric current	ampere	A
Thermodynamic temperature	kelvin	K	(K=°C+273)
Luminous intensity	candela	cd
Amount of substance	mole	mol

SI units may be made larger or smaller by using prefixes which denote multiplication or division by a particular amount. The eight most common multiples, with their meaning, are listed below:

Length is the distance between two points. The standard unit of length is the metre, although the centimetre (cm), millimetre (mm) and kilometre (km), are often used.

Area is a measure of the size or extent of a plane surface and is measured by multiplying a length by a length. If the lengths are in metres then the unit of area is the square metre (m²).

Conversely, 1 cm² = 10⁻⁴ m² and 1 mm² = 10⁻⁶ m².

Volume is a measure of the space occupied by a solid and is measured by multiplying a length by a length by a length. If the lengths are in metres then the unit of volume is in cubic metres (m³).

Conversely, 1 cm³ = 10⁻⁶m³ and 1mm³ = 10⁻⁹m³. Another unit used to measure volume, particularly with liquids, is the litre (l), where 1 litre = 1000 cm³.

Mass is the amount of matter in a body and is measured in kilograms (kg).

and 1 tonne (t) = 1000 kg.

Problem 1. Express (a) a length of 36 mm in metres, (b) 32,400 mm² in square metres, and (c) 8,540,000 mm³ in cubic metres

Hence,

Problem 2. Determine the area of a room 15m long by 8m wide in (a) m², (b) cm², (c) mm²

(Note, it is usual to express the power of 10 as a multiple of 3, i.e. × 10³ or × 10⁶ or × 10⁻⁹ and so on....

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Dedication
• Table of Contents
• Preface
• SECTION I APPLIED MATHEMATICS
• SECTION II MECHANICAL APPLICATIONS
• SECTION III ELECTRICAL APPLICATIONS
• SECTION IV ENGINEERING SYSTEMS
• List of formulae for science for engineering
• Answers to practice exercises
• Glossary of terms
• Index