Shawn Kenny, Ph.D., P.Eng.Assistant ProfessorFaculty of Engineering and Applied ScienceMemorial University of Newfoundlandspkenny@engr.mun.ca

ENGI 1313 Mechanics I

Lecture 01: Course Introduction and GeneralPrinciples

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ENGI 1313 Resources

TextbookEngineering Mechanics Statics and Dynamics, 11th Edition R.C. HibbelerPearson Prentice Hall (ISBN 0-13-221509-8)

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ENGI 1313 Resources

Statics Study PackChapter reviewsAccess to Pearson Prentice Hall website• wps.prenhall.com/

esm_hibbeler_engmech_11

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ENGI 1313 Resources

MUN Engineering Instructor WebsiteCourse information• www.engr.mun.ca/~spkenny/Courses

Professor contact information• www.engr.mun.ca/~spkenny/Contact

Office Hours• Mon. & Wed. (3-5PM)• Other times can be scheduled by appointment

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ENGI 1313 Resources

General Websitesen.wikibooks.org/wiki/Staticswww.mun.ca/orientation/www.etipsforagrades.comwww.studygs.net/

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Academic & Administrative Policies

MUN Engineering WebsiteEngineering exam policy• http://www.engr.mun.ca/undergrad/

MUN WebsiteUniversity regulations• http://www.mun.ca/regoff/calendar/

Student policies• http://www.mun.ca/student/policies/

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Course Schedule

LecturesDay: Mon., Tue., Wed. & FriTime: 0900-0950 Location: IIC2001

No LecturesOct. 8 & 9 Fall BreakNov. 12 Remembrance Day

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Planned Lecture Schedule

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Course Perspective

Educational ProcessCritical thinkingMaking mistakesAsking questionsLearningApplying knowledgeEngagementProfessional development

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Course Perspective

Fundamental Engineering CourseMechanicsFoundation to build upon

Work EthicRegular study habits• Lecture and tutorial schedule is known

Critical thinking & problem solving…Critical thinking & problem solving

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Objective of the Lecture Notes

to explicitly follow the textbookto provide complement the textbook by providing additional worked examplesto occasionally present complementary material that illustrates practical engineering applications of the theory

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Lecture 01 Objectives

to introduce field of mechanicsto introduce some fundamental conceptsto review units of measurement and systemsto provide guidance on engineering calculation procedures and analysis

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Introduction to Mechanics

Mechanics

Rigid BodyMechanics

DeformationMechanics

FluidMechanics

• Statics• Dynamics

This course only examinesRigid Body Mechanics: Statics

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General Principles

StaticsEffect of loads on bodies in static equilibrium• Balanced loads• At rest or under motion at constant velocity

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General Principles

KinematicsEffect of motion without consideration of loads

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General Principles

DynamicsEffect of loads on bodies in motion• Unbalanced loads• Acceleration

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Brief Historical Perspective

Engineering Mechanics and PrinciplesGeometryEmpirical

Societal ApplicationsMilitaryCivilianShipbuilding

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Simple Machines

Inclined planeWedgeScrew

LeverPulleyWheel and axle

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Simple Machines

Inclined Plane

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Simple Machines

Lever

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Simple Machines

Lever

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Fundamental Concepts

IdealizationsParticle• Constant mass• Negligible size

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Fundamental Concepts

IdealizationsRigid Body• Combination of particles• Finite size• Relative position of

particles remain fixed• No internal deformation

Deformable Body

P P

Rigid Body

P P

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Fundamental Concepts

IdealizationsConcentrated Force• Load effects acting

at a point on a body• Load acts on small

dimensions relative to body size

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Fundamental Concepts

Newton’s Laws of MotionBasis of classical mechanicsMotion ≡ Momentum

• Massive, rigid body• Empirical• Inertial reference frame

(no acceleration)

vmprr

=

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Fundamental Concepts

Newton’s 1st Law – InertiaParticle equilibrium• Rest• Constant velocity

Unbalanced forces• External• Change in velocity, acceleration

F1

F2

F3

V = 0, v

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Fundamental Concepts

Newton’s 2nd Law – AccelerationObject in motionUnbalanced external forcesAcceleration• Proportional to force magnitude• Direction of applied net unbalanced force

( ) amvmdtdF

rrr==

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Fundamental Concepts

Newton’s 3rd Law – Reciprocal ActionAction ⇒ ⇐ Reaction• To every action

there is an equal and opposite reaction

• Equal force magnitude

• Opposite force sense or direction

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Fundamental Concepts

Newton’s Law of Gravitational Attraction

Point-to-point mass attraction through centers• Force ∝ point mass

1 / distance2

221

rmmGF =

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Fundamental Concepts

WeightForce acting on particle due to gravityg = acceleration due to gravity• Varies altitude, latitude ⇒ not absolute• Standard is 9.80665 m/s2

gmrmmGW 2

e ==

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Fundamental ConceptsPhysical Quantities

Characteristics• Measurement process• System of units

Length (L)• Distance, size• Relative position of points in space

Time (T)• Sequence or succession of events

Mass (M)• Intrinsic property of matter• Relative action between bodies

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Fundamental Concepts

ForcesType• Direct contact• Electromagnetic• Gravitational

Characteristics• Magnitude• Direction• Point of application

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Units of Measurement

Standardized Quantity Physical PropertyScientific method ⇔ reproducibleEconomic and scientific drivers

Historical ContextHuman body• Examples: digit, palm, cubit

Variability• Examples: Arabic, Egyptian, Greek, Roman

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Units of Measurement

International System of UnitsUnified, rational system • Units of measurement• Decimal system

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Units of Measurement

Imperial and US CustomarySimilarities and differencesMultiple units of measurement• Length ⇒ inch, foot, chain, furlong• Mass ⇒ grain, ounce, pound,

Relatively more complex rules for conversion• 12 inches = 1 foot• 5280 feet = 1 mile• 16 ounces = 1 pound (mass)

Confusion on units• Pound force versus pound mass

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Units of Measurement

Base UnitsFundamental structure for the system of units • SI ⇒ meter (m), kilogram (kg), second (s)• FPS ⇒ foot (ft), pound (lb), second (s)

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Units of Measurement

Derived UnitsPhysical lawsBase units

Compound UnitsArea, volume

M⋅L2⋅T-2kg⋅m2⋅s-2PaPressureM⋅L⋅T-2kg⋅m⋅s-2NForce

M⋅L-1⋅T-2kg⋅m-1⋅s-2JEnergy

DimensionBase UnitsSymbolQuantity

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Engineering Calculations

Significant Figures and RoundingMeasurement tools and error• Basis of engineering data• Precision versus accuracy

Computational tools• Numerical precision • Constants (e.g. e, π)

Consistent Use• Measurement ⇒ meters• Reporting ⇒ millimeters

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Engineering AnalysisProblem Statement

ObjectiveData and diagramsKnown and unknown quantities

Applicable TheoryAssumptions, limitations and constraints

Problem SolutionDimensionally homogeneous, consistent unitsSignificant figures and rounding

AssessmentEngineering judgment, common sense

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Representative Problems

Hibbeler (2007) Textbook

Study PackReview questions 1 to 8

5-10minEasy1-1 to 1-1610-15minMedium1-17 to 1-20

Estimated TimeDegree of DifficultyProblem Set

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ReferencesHibbeler (2007)http://wps.prenhall.com/esm_hibbeler_engmech_1http://en.wikipedia.orgwww.royalwwc2007.comhttp://www.liebherr.com/lh/www.ultimaterollercoaster.comhttp://www.rlphotos.com/http://www.world-mysteries.com/gw_tb_gp.htmhttp://www.starlight-theatre.ca/images/013.JPGhttp://www.slrugby.com