BASICS OF MECHANICAL
ENGINEERING:
INTEGRATING SCIENCE, TECHNOLOGY
AND COMMON SENSE
, Table of contents
TABLE OF CONTENTS II
FOREWORD IV
NOMENCLATURE VII
UNITS CONVERSIONS IX
CHAPTER 1. WHAT IS MECHANICAL ENGINEERING? 1
CHAPTER 2. UNITS 4
Base units 4
Derived units 6
Special consideration 1: pounds force vs. pounds mass 6
Special consideration 2: temperature 7
Examples of the use (and power) of units 8
CHAPTER 3. “ENGINEERING SCRUTINY” 11
Scrutinizing analytical formulas and results 11
Scrutinizing computer solutions 13
Examples of the use of units and scrutiny 14
CHAPTER 4. FORCES IN STRUCTURES 20
Forces 20
Degrees of freedom 20
Moments of forces 22
Types of forces and moments of force 24
Analysis of statics problems 27
CHAPTER 5. STRESSES, STRAINS AND MATERIAL PROPERTIES 36
Stresses and strains 36
Principal stresses and maximum shear stress 42
Pressure vessels 47
Bending of beams 49
Buckling of columns 56
CHAPTER 6. FLUID MECHANICS 58
Fluid statics 58
Equations of fluid motion 61
Bernoulli’s equation 61
Conservation of mass 63
Viscous effects 64
Definition of viscosity 64
No-slip boundary condition 65
ii
, Reynolds number 65
Navier-Stokes equations 67
Laminar and turbulent flow 68
Lift, drag and fluid resistance 69
Lift and drag coefficients 69
Flow around spheres and cylinders 69
Flow through pipes 73
Compressible flow 76
CHAPTER 7. THERMAL AND ENERGY SYSTEMS 81
Conservation of energy – First Law of Thermodynamics 81
Describing a thermodynamic system 81
Statement of the First Law 81
Equations for conservation of energy for a control mass 81
Equations for conservation of energy for a control volume 84
Processes 86
Examples of energy analysis using the 1st Law 87
Second Law of thermodynamics 90
Engines cycles and efficiency 91
Heat transfer 97
Conduction 97
Convection 98
Radiation 99
CHAPTER 8. WRITTEN AND ORAL COMMUNICATION 101
APPENDIX A. DESIGN PROJECTS 107
Generic information about the design projects 107
How to run a meeting (PDR’s philosophy…) 107
Suggestions for the written report 107
King of the Hill 110
Arduino Cars 116
3D-Printed Bridge 119
APPENDIX B. PROBLEM-SOLVING METHODOLOGY 124
APPENDIX C. EXCEL TUTORIAL 125
APPENDIX D. STATISTICS 128
Mean and standard deviation 128
Stability of statistics 129
Least-squares fit to a set of data 130
iii
, Foreword
If you’re reading this book, you’re probably already enrolled in an introductory university course
in Mechanical Engineering. The primary goals of this textbook are, to provide you, the student,
with:
1. An understanding of what Mechanical Engineering is and to a lesser extent what it is not
2. Some useful tools that will stay with you throughout your engineering education and career
3. A brief but significant introduction to some of the major topics of Mechanical Engineering
and enough understanding of these topics so that you can relate them to each other
4. A sense of common sense
The challenge is to accomplish these objectives without overwhelming you so much that you won’t
be able to retain the most important concepts.
In regards to item 2 above, I remember nothing about some of my university courses, even in
cases where I still use the information I learned therein. In others I remember “factoids” that I still
use. One goal of this textbook is to provide you with a set of useful factoids so that even if you
don’t remember any specific words or figures from this text, and don’t even remember where you
learned these factoids, you still retain them and apply them when appropriate.
In regards to item 3 above, in particular the relationships between topics, this is one area where I
feel engineering faculty (myself included) do not do a very good job. Time and again, I find that
students learn something in class A, and this information is used with different terminology or in a
different context in class B, but the students don’t realize they already know the material and can
exploit that knowledge. As the old saying goes, “We get too soon old and too late smart…”
Everyone says to themselves several times during their education, “oh… that’s so easy… why didn’t
the book [or instructor] just say it that way…” I hope this text will help you to get smarter sooner
and older later.
A final and less tangible purpose of this text (item 4 above) is to try to instill you with a sense of
common sense. Over my 33 years of teaching at the university level, I have found that students
have become more technically skilled and well-rounded but have less ability to think and figure out
things for themselves. I attribute this in large part to the fact that when I was a teenager, cars were
relatively simple and my friends and I spent hours working on them. When our cars weren’t broken,
we would sabotage (nowadays “hack” might be a more descriptive term) each other’s cars. The best
hacks were those that were difficult to diagnose, but trivial to fix once you figured out what was
wrong. We learned a lot of common sense working on cars. Today, with electronic controls, cars
are very difficult to work on or hack. Even with regards to electronics, today the usual solution to a
broken device is to throw it away and buy a newer device, since the old one is probably nearly
obsolete by the time it breaks. Of course, common sense per se is probably not teachable, but a sense
of common sense, that is, to know when it is needed and how to apply it, might be teachable. If I may
be allowed an immodest moment in this textbook, I would like to give an anecdote about my son
Peter. When he was not quite 3 years old, like most kids his age had a pair of shoes with lights
(actually light-emitting diodes or LEDs) that flash as you walk. These shoes work for a few months
until the heel switch fails (usually in the closed position) so that the LEDs stay on continuously for a
day or two until the battery goes dead. One morning he noticed that the LEDs in one of his shoes
were on continuously. He had a puzzled look on his face but said nothing. Instead, he went to look
for his other shoe, and after rooting around a bit, found it. He then picked it up, hit it against
iv
ENGINEERING:
INTEGRATING SCIENCE, TECHNOLOGY
AND COMMON SENSE
, Table of contents
TABLE OF CONTENTS II
FOREWORD IV
NOMENCLATURE VII
UNITS CONVERSIONS IX
CHAPTER 1. WHAT IS MECHANICAL ENGINEERING? 1
CHAPTER 2. UNITS 4
Base units 4
Derived units 6
Special consideration 1: pounds force vs. pounds mass 6
Special consideration 2: temperature 7
Examples of the use (and power) of units 8
CHAPTER 3. “ENGINEERING SCRUTINY” 11
Scrutinizing analytical formulas and results 11
Scrutinizing computer solutions 13
Examples of the use of units and scrutiny 14
CHAPTER 4. FORCES IN STRUCTURES 20
Forces 20
Degrees of freedom 20
Moments of forces 22
Types of forces and moments of force 24
Analysis of statics problems 27
CHAPTER 5. STRESSES, STRAINS AND MATERIAL PROPERTIES 36
Stresses and strains 36
Principal stresses and maximum shear stress 42
Pressure vessels 47
Bending of beams 49
Buckling of columns 56
CHAPTER 6. FLUID MECHANICS 58
Fluid statics 58
Equations of fluid motion 61
Bernoulli’s equation 61
Conservation of mass 63
Viscous effects 64
Definition of viscosity 64
No-slip boundary condition 65
ii
, Reynolds number 65
Navier-Stokes equations 67
Laminar and turbulent flow 68
Lift, drag and fluid resistance 69
Lift and drag coefficients 69
Flow around spheres and cylinders 69
Flow through pipes 73
Compressible flow 76
CHAPTER 7. THERMAL AND ENERGY SYSTEMS 81
Conservation of energy – First Law of Thermodynamics 81
Describing a thermodynamic system 81
Statement of the First Law 81
Equations for conservation of energy for a control mass 81
Equations for conservation of energy for a control volume 84
Processes 86
Examples of energy analysis using the 1st Law 87
Second Law of thermodynamics 90
Engines cycles and efficiency 91
Heat transfer 97
Conduction 97
Convection 98
Radiation 99
CHAPTER 8. WRITTEN AND ORAL COMMUNICATION 101
APPENDIX A. DESIGN PROJECTS 107
Generic information about the design projects 107
How to run a meeting (PDR’s philosophy…) 107
Suggestions for the written report 107
King of the Hill 110
Arduino Cars 116
3D-Printed Bridge 119
APPENDIX B. PROBLEM-SOLVING METHODOLOGY 124
APPENDIX C. EXCEL TUTORIAL 125
APPENDIX D. STATISTICS 128
Mean and standard deviation 128
Stability of statistics 129
Least-squares fit to a set of data 130
iii
, Foreword
If you’re reading this book, you’re probably already enrolled in an introductory university course
in Mechanical Engineering. The primary goals of this textbook are, to provide you, the student,
with:
1. An understanding of what Mechanical Engineering is and to a lesser extent what it is not
2. Some useful tools that will stay with you throughout your engineering education and career
3. A brief but significant introduction to some of the major topics of Mechanical Engineering
and enough understanding of these topics so that you can relate them to each other
4. A sense of common sense
The challenge is to accomplish these objectives without overwhelming you so much that you won’t
be able to retain the most important concepts.
In regards to item 2 above, I remember nothing about some of my university courses, even in
cases where I still use the information I learned therein. In others I remember “factoids” that I still
use. One goal of this textbook is to provide you with a set of useful factoids so that even if you
don’t remember any specific words or figures from this text, and don’t even remember where you
learned these factoids, you still retain them and apply them when appropriate.
In regards to item 3 above, in particular the relationships between topics, this is one area where I
feel engineering faculty (myself included) do not do a very good job. Time and again, I find that
students learn something in class A, and this information is used with different terminology or in a
different context in class B, but the students don’t realize they already know the material and can
exploit that knowledge. As the old saying goes, “We get too soon old and too late smart…”
Everyone says to themselves several times during their education, “oh… that’s so easy… why didn’t
the book [or instructor] just say it that way…” I hope this text will help you to get smarter sooner
and older later.
A final and less tangible purpose of this text (item 4 above) is to try to instill you with a sense of
common sense. Over my 33 years of teaching at the university level, I have found that students
have become more technically skilled and well-rounded but have less ability to think and figure out
things for themselves. I attribute this in large part to the fact that when I was a teenager, cars were
relatively simple and my friends and I spent hours working on them. When our cars weren’t broken,
we would sabotage (nowadays “hack” might be a more descriptive term) each other’s cars. The best
hacks were those that were difficult to diagnose, but trivial to fix once you figured out what was
wrong. We learned a lot of common sense working on cars. Today, with electronic controls, cars
are very difficult to work on or hack. Even with regards to electronics, today the usual solution to a
broken device is to throw it away and buy a newer device, since the old one is probably nearly
obsolete by the time it breaks. Of course, common sense per se is probably not teachable, but a sense
of common sense, that is, to know when it is needed and how to apply it, might be teachable. If I may
be allowed an immodest moment in this textbook, I would like to give an anecdote about my son
Peter. When he was not quite 3 years old, like most kids his age had a pair of shoes with lights
(actually light-emitting diodes or LEDs) that flash as you walk. These shoes work for a few months
until the heel switch fails (usually in the closed position) so that the LEDs stay on continuously for a
day or two until the battery goes dead. One morning he noticed that the LEDs in one of his shoes
were on continuously. He had a puzzled look on his face but said nothing. Instead, he went to look
for his other shoe, and after rooting around a bit, found it. He then picked it up, hit it against
iv
