
Mechanical Engineering Principles
Mechanical Engineering Principles
Second Edition
Why are competent engineers so vital?
Engineering is among the most important of all professions. It is the authors’ opinions that engineers save
more lives than medical doctors (physicians). For example, poor water or the lack of it, is the second largest
cause of human death in the world, and if engineers are given the tools, they can solve this problem. The
largest cause of human death is caused by the malarial mosquito, and even death due to malaria can be
decreased by engineers  by providing helicopters for spraying areas infected by the mosquito and making and
designing medical syringes and pills to protect people against catching all sorts of diseases. Most medicines
are produced by engineers! How does the engineer put 1 mg of ‘medicine’ precisely and individually into
millions of pills, at an affordable price?
Moreover, one of the biggest contributions by humankind was the design of the agricultural tractor, which
was designed and built by engineers to increase food production manyfold for a human population which
moreorless quadruples every century! It is also interesting to note that the richest countries in the world are
very heavily industrialised. Engineers create wealth! Most other professions don’t!
Even in blue sky projects, engineers play a major role. For example, most rocket scientists are chartered
engineers or their equivalents and Americans call their Chartered Engineers (and their equivalents), scientists.
Astronomers are space scientists and not rocket scientists; they could not design a rocket to conquer outer
space. Even modern theoretical physicists are mainly interested in astronomy and cosmology and also nuclear
science. In general a theoretical physicist cannot, without special training, design a submarine structure to
dive to the bottom of the Mariana Trench, which is 11.52 km or 7.16 miles deep, or design a very long bridge,
a tall city skyscraper or a rocket to conquer outer space.
This book presents a solid foundation for the reader in mechanical engineering principles, on which s/he
can safely build tall buildings and long bridges that may last for a thousand years or more. It is the authors’
experience that it is most unwise to attempt to build such structures on shaky foundations; they may come
tumbling down  with disastrous consequences.
John O. Bird is the former Head of Applied Electronics in the Faculty of Technology at Highbury College,
Portsmouth, U.K. More recently, he has combined freelance lecturing at the University of Portsmouth, with Examiner
responsibilities for Advanced Mathematics with City & Guilds, and examining for the International Baccalaureate
Organisation. He is the author of some 120 textbooks on engineering and mathematical subjects with worldwide sales
approaching 1 million copies. He is currently a Senior Training Provider at the Royal Naval School of Marine
Engineering in the Defence College of Marine and Air Engineering at H.M.S. Sultan, Gosport, Hampshire, U.K.
Carl T. F. Ross gained his ﬁ rst degree in Naval Architecture, from King’s College, Durham University; his PhD in
Structural Engineering from the Victoria University of Manchester; and was awarded his DSc in Ocean Engineering
from the CNAA, London. His research in the ﬁ eld of engineering led to advances in the design of submarine pressure
hulls. His publications to date exceed some 270 papers and books and he is Professor of Structural Dynamics at the
University of Portsmouth, U.K.
See Carl Ross’s website below, which has an enormous content on science, technology and education.
http://homepage.ntlworld.com/carl.ross/page3.htm Mechanical Engineering Principles
Second Edition
John O. Bird, BSc(Hons), CEng, CMath, CSci, FIMA, FITE, FCollT
Carl T. F. Ross, BSc(Hons), PhD, DSc, CEng, FRINA, MSNAME Second edition published 2012
by Routledge
2 Park Square, Milton Park, Abingdon, Oxon OX14 4RN
Simultaneously published in the USA and Canada
by Routledge
711 Third Avenue, New York, NY 10017
Routledge is an imprint of the Taylor & Francis Group, an informa business
© 2012 John O. Bird and Carl T. F. Ross
The right of John O. Bird and Carl T. F. Ross to be identified as authors of this work has been asserted by them in
accordance with sections 77 and 78 of the Copyright, Designs and Patents Act 1988.
All rights reserved. No part of this book may be reprinted or reproduced or utilised in any form or by any electronic,
mechanical, or other means, now known or hereafter invented, including photocopying and recording, or in any
information storage or retrieval system, without permission in writing from the publishers.
This publication presents material of a broad scope and applicability. Despite stringent efforts by all concerned in the
publishing process, some typographical or editorial errors may occur, and readers are encouraged to bring these to our
attention where they represent errors of substance. The publisher and author disclaim any liability, in whole or in part,
arising from information contained in this publication. The reader is urged to consult with an appropriate licensed
professional prior to taking any action or making any interpretation that is within the realm of a licensed professional
practice.
First edition published by Elsevier in 2002
Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for
identification and explanation without intent to infringe.
British Library Cataloguing in Publication Data
A catalogue record for this book is available from the British Library
Library of Congress Cataloguing in Publication Data
A catalog record for this title has been requested
ISBN: 9780415517850 (pbk)
ISBN: 9780203121146 (ebk)
Typeset in Times
by RefineCatch Limited, Bungay, Suffolk Contents
Preface ix 4.3 Forces 47
4.4 The resultant of two coplanar forces 48
4.5 Triangle of forces method 48
Part One Revision of Mathematics 1
4.6 The parallelogram of forces method 50
4.7 Resultant of coplanar forces by
1 Revisionary Mathematics 3
calculation 50
1.1 Introduction 3
4.8 Resultant of more than two
1.2 Radians and degrees 3
coplanar forces 51
1.3 Measurement of angles 4
4.9 Coplanar forces in equilibrium 53
1.4 Triangle calculations 5
4.10 Resolution of forces 54
1.5 Brackets 7
4.11 Summary 58
1.6 Fractions 8
1.7 Percentages 9 5 Simply supported beams 61
1.8 Laws of indices 11 5.1 The moment of a force 61
1.9 Simultaneous equations 14 5.2 E quilibrium and the principle of
moments 62
Revision Test 1 Revisionary mathematics 18 5.3 S imply supported beams
having point loads 64
5.4 Simply supported beams with couples 68
Part Two Statics and Strength
Revision Test 2 F orces, tensile testing
of Materials 21
and beams 72
2 The effects of forces on materials 23
2.1 Introduction 23 6 Forces in structures 73
2.2 Tensile force 24 6.1 Introduction 73
2.3 Compressive force 24 6.2 W orked problems on mechanisms
2.4 Shear force 24 and pinjointed trusses 74
2.5 Stress 24 6.3 Graphical method 75
2.6 Strain 25 6.4 Method of joints
2.7 E lasticity, limit of proportionality (a mathematical method) 79
and elastic limit 27 6.5 The method of sections
2.8 Hooke’s law 28 (a mathematical method) 84
2.9 Ductility, brittleness and malleability 32
2.10 Modulus of rigidity 32 7 Bending moment and shear force diagrams 87
2.11 Thermal strain 33 7.1 Bending moment (M) 87
2.12 Compound bars 33 7.2 Shearing force (F) 87
7.3 Worked problems on bending
3 Tensile testing 39 moment and shearing force diagrams 88
3.1 The tensile test 39 7.4 Uniformly distributed loads 97
3.2 Worked problems on tensile testing 40
3.3 Further worked problems on 8 First and second moments of areas 102
tensile testing 42 8.1 Centroids 102
3.4 Proof stress 44 8.2 The first moment of area 102
8.3 C entroid of area between a curve
4 Forces acting at a point 46 and the xaxis 103
4.1 Scalar and vector quantities 46 8.4 C entroid of area between a
4.2 Centre of gravity and equilibrium 46 curve and the yaxis 103 vi Contents
8.5 W orked problems on centroids of 14.4 Rotation of a rigid body about a fixed axis 167
simple shapes 104 14.5 Moment of inertia (I) 167
8.6 F urther worked problems on centroids
of simple shapes 105 15 Work, energy and power 170
8.7 S econd moments of area of 15.1 Work 170
regular sections 106 15.2 Energy 174
8.8 S econd moment of area for 15.3 Power 175
‘builtup’ sections 113 15.4 Potential and kinetic energy 178
15.5 Kinetic energy of rotation 181
Revision Test 3 Forces in structures,
bending moment and shear Revision Test 5 L inear and angular motion,
force diagrams, and second m omentum and impulse,
moments of area 119 force, mass and acceleration,
work, energy and power 184
9 Bending of beams 120
9.1 Introduction 120 16 Friction 185
9.2 To prove that s = M = E 121 16.1 Introduction to friction 185
y I R
16.2 Coefficient of friction 186
9.3 W orked problems on the bending
16.3 Applications of friction 187
of beams 122
16.4 Friction on an inclined plane 188
16.5 M otion up a plane with the pulling
10 Torque 126
force P parallel to the plane 188
10.1 Couple and torque 126
16.6 M otion down a plane with the
10.2 W ork done and power transmitted
pulling force P parallel to the plane 189
by a constant torque 127
16.7 M otion up a plane due to a horizontal
10.3 Kinetic energy and moment of inertia 129
force P 189
10.4 Power transmission and efficiency 132
16.8 The efficiency of a screw jack 192
11 Twisting of shafts 136
17 Motion in a circle 196
t T Gθ
11.1 To prove that = = 136 17.1 Introduction 196
r J L
17.2 Motion on a curved banked track 198
11.2 Worked problems on the
17.3 Conical pendulum 199
twisting of shafts 138
17.4 Motion in a vertical circle 201
17.5 Centrifugal clutch 203
Revision Test 4 Bending of beams, torque
and twisting of shafts 142
18 Simple harmonic motion 205
18.1 Introduction to simple
harmonic motion (SHM) 205
Part Three Dynamics 143 18.2 The springmass system 206
18.3 The simple pendulum 208
12 Linear and angular motion 145 18.4 The compound pendulum 209
12.1 The radian 145 18.5 Torsional vibrations 210
12.2 Linear and angular velocity 145
12.3 Linear and angular acceleration 147 19 Simple machines 212
12.4 Further equations of motion 148 19.1 Machines 212
12.5 Relative velocity 150 19.2 F orce ratio, movement ratio and efficiency 212
19.3 Pulleys 214
13 Linear momentum and impulse 154 19.4 The screwjack 216
13.1 Linear momentum 154 19.5 Gear trains 216
13.2 Impulse and impulsive forces 157 19.6 Levers 218
14 Force, mass and acceleration 162 Revision Test 6 Friction, motion in a circle,
14.1 Introduction 162 simple harmonic motion and
14.2 Newton’s laws of motion 163 simple machines 222
14.3 Centripetal acceleration 165 Contents vii
23.4 Flow nozzle 263
Part Four Heat Transfer and Fluid 23.5 Pitotstatic tube 263
Mechanics 223 23.6 Mechanical flowmeters 264
23.7 Deflecting vane flowmeter 264
20 Heat energy and transfer 225 23.8 Turbine type meters 264
20.1 Introduction 225 23.9 Float and taperedtube meter 265
20.2 The measurement of temperature 226 23.10 Electromagnetic flowmeter 266
20.3 Specific heat capacity 226 23.11 Hotwire anemometer 266
20.4 Change of state 228 23.12 Choice of flowmeter 267
20.5 Latent heats of fusion and vaporisation 229 23.13 Equation of continuity 267
20.6 A simple refrigerator 231 23.14 Bernoulli’s equation 267
20.7 Conduction, convection and radiation 231 23.15 Impact of a jet on a stationary plate 269
20.8 Vacuum flask 232
20.9 Use of insulation in conserving fuel 232 24 Ideal gas laws 272
24.1 Boyle’s law 272
21 Thermal expansion 235 24.2 Charles’ law 273
21.1 Introduction 235 24.3 The pressure law 274
21.2 P ractical applications of 24.4 Dalton’s law of partial pressure 275
thermal expansion 235 24.5 Characteristic gas equation 275
21.3 Expansion and contraction of water 236 24.6 Worked problems on the
21.4 Coefficient of linear expansion 236 characteristic gas equation 275
21.5 Coefficient of superficial expansion 238 24.7 Further worked problems on the
21.6 Coefficient of cubic expansion 239 characteristic gas equation 277
25 The measurement of temperature 281
Revision Test 7 Heat energy and transfer,
25.1 Liquidinglass thermometer 281
and thermal expansion 243
25.2 Thermocouples 282
25.3 Resistance thermometers 284
22 Hydrostatics 244 25.4 Thermistors 286
22.1 Pressure 244 25.5 Pyrometers 286
22.2 Fluid pressure 245 25.6 T emperature indicating paints
22.3 Atmospheric pressure 247 and crayons 287
22.4 Archimedes’ principle 248 25.7 Bimetallic thermometers 288
22.5 Measurement of pressure 249 25.8 Mercuryinsteel thermometer 288
22.6 Barometers 249 25.9 Gas thermometers 288
22.7 Absolute and gauge pressure 251 25.10 Choice of measuring devices 288
22.8 The manometer 252
22.9 The Bourdon pressure gauge 253 Revision Test 8 Hydrostatics, fluid flow,
22.10 Vacuum gauges 253 gas laws and temperature
22.11 Hydrostatic pressure on measurement 290
submerged surfaces 254
22.12 Hydrostatic thrust on curved surfaces 255
A list of formulae for mechanical
22.13 Buoyancy 255
engineering principles 291
22.14 The stability of floating bodies 255
Greek alphabet 296
23 Fluid flow 261
23.1 Differential pressure flowmeters 261 Answers to multiplechoice questions 297
23.2 Orifice plate 262
23.3 Venturi tube 262 Index 299 Preface
Mechanical Engineering Principles 2nd Edition aims Although prerequisites for the modules covered
to broaden the reader’s knowledge of the basic principles in this book include Foundation Certificate/ diploma,
that are fundamental to mechanical engineering design or similar, in Mathematics and Science, each topic
and the operation of mechanical systems. considered in the text is presented in a way that
assumes that the reader has little previous
Modern engineering systems and products still rely
knowledge of that topic.
upon static and dynamic principles to make them work.
Even systems that appear to be entirely electronic have a Mechanical Engineering Principles 2nd Edition
physical presence governed by the principles of statics. contains over 325 worked problems, followed by
In this second edition of Mechanical Engineering over 550 further problems (all with answers).
Principles, a chapter has been added on revisionary The further problems are contained within some
mathematics; it is not possible to progress in engineering 140 Exercises; each Exercise follows on directly
studies without a reasonable knowledge of mathematics, from the relevant section of work, every few
a fact that soon becomes obvious to both students and pages. In addition, the text contains 276 multiple
teachers alike. It is therefore hoped that this chapter on choice questions (all with answers), and 260 short
basic mathematics revision will be helpful and make answer questions, the answers for which can be
the engineering studies more comprehensible. Minor determined from the preceding material in that particular
modifications and some further worked problems have chapter. Where at all possible, the problems mirror
also been added throughout the text. practical situations found in mechanical engineering.
371 line diagrams enhance the understanding of the
Free Internet downloads of full solutions to the fur
theory.
ther problems and a PowerPoint presentation of all
the illustrations contained in the text is available – see At regular intervals throughout the text are some
page x. 8 Revision Tests to check understanding. For example,
Revision Test 1 covers material contained in Chapter
For clarity, the text is divided into four parts, these
1, Test 2 covers the material in Chapters 2 to 5, and
being:
so on. No answers are given for the questions in the
Part 1 Revision of Mathematics Revision Tests, but a Lecturer’s guide has been
Part 2 Statics and strength of materials produced giving full solutions and suggested marking
Part 3 Dynamics scheme. The guide is offered online free to lecturer’s/
Part 4 Heat transfer and fluid mechanics instructor’s – see below.
Mechanical Engineering Principles 2nd Edition is At the end of the text, a list of relevant formulae is
suitable for the following: included for easy reference.
(i) National Certificate/Diploma courses in ‘Learning by Example’ is at the heart of Mechanical
Mechanical Engineering Engineering Principles, 2nd Edition.
(ii) Undergraduate courses in Mechanical,
Civil, Structural, Aeronautical & Marine JOHN BIRD
Engineering, together with Naval Architecture Royal Naval School of Marine Engineering,
(iii) Any introductory/access/foundation course HMS Sultan, formerly
involving Mechanical Engineering Principles University of Portsmouth and Highbury
at University, and Colleges of Further and College, Portsmouth
Higher education. CARL ROSS Professor, University of Portsmouth
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