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Namas ChandraIntroduction to Mechanical engineering
HibblerChapter 1-1
EML 3004C
CHAPTER ONE
General Principles
Namas ChandraIntroduction to Mechanical engineering
HibblerChapter 1-2
EML 3004C
Statics, Dynamics and Mechanics of Materials
Statics deals with the state of rest or motion of bodies with constant velocities
In dynamics, the bodies are allowed to accelerate. Two Branches of static equilibrium
Statics Mechanics of Materials
Statics
Equilibrium of Bodies-material independent, uses only static equations
Mechanics of Materials
Relationship between the external loads, the intensity of internal forces and its deformation response
0F M F M ma
0F M
Namas ChandraIntroduction to Mechanical engineering
HibblerChapter 1-3
EML 3004C
Basic Concepts
Quantities
Length (location, position, size)
Time (succession of events)
Force (Push, Pull)
Mass (Properties of Matter) ONLY THREE OF FOUR NEEDED (NEWTONS LAW)
Idealization
Particle (neglect, size, geometry)
Rigid Body (all points within remain in the same position, at fixed distances from each other)
Concentrated Force ( over a very small area, zero)
Namas ChandraIntroduction to Mechanical engineering
HibblerChapter 1-4
EML 3004C
Physical Quantities
Physical Qualities
Mass,
Force
time
distance,
Density
Temperature
Volume
area
length
displacement
velocity
acceleration
Namas ChandraIntroduction to Mechanical engineering
HibblerChapter 1-5
EML 3004C
Scalar Quantities Described by their magnitude, mass (italic form) or lower case (a for A)
Vector Quantities Described by a magnitude, a direction, and a point of
application (Bold Face) in the book Bar or Arrow in handwritten work Magnitude or A (italic) or a =
Scalar and Vector Quantities
A,A
A A
R
R
Namas ChandraIntroduction to Mechanical engineering
HibblerChapter 1-6
EML 3004C
Newton’s Laws
Newton’s First Law
A body at rest tends to remain at rest & a body in motion at a constant velocity will tend to maintain the velocity.
Newton’s Second Law
Change of motion is proportional to the moving force impressed and takes place in the direction of the straight line in which such force is impressed.
F ma
Namas ChandraIntroduction to Mechanical engineering
HibblerChapter 1-7
EML 3004C
Newton’s Laws
Consequences of Newton’s Third Law
When two bodies interact, a pair of equal and opposite reaction forces will exist at their contact point.
This force pair will have the same magnitude and acts along the same direction, but have opposite sense.
The mutual force of action and reaction between two bodies are equal, opposite, and collinear.
Kg = mass=[m] Newton = Force=[F]Slug= mass =[m] lbf = Force = [F]
Namas ChandraIntroduction to Mechanical engineering
HibblerChapter 1-8
EML 3004C
Gravitational Law
G = universal constant of gravitation
m1,m2 = mass of each of the two particlesr= distance
Gravitational Law
221
r
mmGF
2
3121073.66skg
m
Namas ChandraIntroduction to Mechanical engineering
HibblerChapter 1-9
EML 3004C
WeightIf = mass of the particle
= mass of the earthr = distance of the particle to the earth’s centerW = weight of the particle
if
What is weight?
1 22
m mW G
r
22
r
Gmg mgW
1m2m
Namas ChandraIntroduction to Mechanical engineering
HibblerChapter 1-10
EML 3004C
SI (International System of Units) Meter (m) Second (sec) Kilogram (kg) Newton (N)
Units
Units Length, time, mass, force -
basic quantities
amF
2
kg mN
s
281.9 smg
mgW
(Note: we use bars to denote forces or vectors)
W = 9.81N
Ex : mass = 1kg
Namas ChandraIntroduction to Mechanical engineering
HibblerChapter 1-11
EML 3004C
Conversion of Units
Conversion of Units
FPS SIForce 1 lb = 4.4482 NMass 1 slug = 14.5938 kgLength 1 ft = 0.3048 m
Ex:2 1000 1 0.3048
21 4.4482 1
kN N lb mkNm m kN N ft
Namas ChandraIntroduction to Mechanical engineering
HibblerChapter 1-12
EML 3004C
CHAPTER ONE.. concludes
General Principles
