ERT 146
Engineering Mechanics
Ms Siti Kamariah Md Sa’at
School of Bioprocess Engineering, UniMAP
sitikamariah@unimap.edu.my
Course Content
Static
 This course covers vector representation of forces,
moments and couples of static equilibrium of
particles, rigid bodies, and engineering
structures, together with analysis of external and
internal forces in structures via the methods of freebody diagrams and properties of cross-sectional
areas.
Dynamic
 In addition, the course also elaborates on kinematics
and kinetics of system of particles and of rigid
bodies in two and three-dimensional spaces covering
force and acceleration, linear and angular
momentum, and energy conservation.
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
Course Outcomes
 Ability to apply the basic principles of statics
and dynamics on mechanism and bodies.
 Ability to analyze systems/problems related
to forces, loads, displacement for bodies at
rest.
 Ability to analyze systems/problems related
to forces, loads, displacement, velocity and
acceleration of bodies in motion.
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
Evaluation

Peperiksaan/ Examination: 70%




Mid Term Examination 1
Mid Term Examination 2
Final Examination
= 10%
= 10%
= 60%
(ii) Kerja kursus/course work: 20%

Assignment/Quiz
= 20%
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
Text Book
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
Chapter 1
Introduction & General
Principles
World highest
building
Burj Dubai
828 m
Taipei 101
509 m
Shanghai World
Financial Center
492 m
International Commerce Centre
(Hong Kong, China)
483m
KLCC
442 m
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
1.1 Mechanics
 Mechanics can be divided into 3 branches:
- Rigid-body Mechanics
- Deformable-body Mechanics
- Fluid Mechanics (2nd year)
 Rigid-body Mechanics deals with
- Statics
- Dynamics
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
1.1 Mechanics
 Statics – Equilibrium of bodies
 At rest
 Move with constant velocity
• Dynamics – Accelerated motion of bodies
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
1.2 Fundamentals Concepts
Basic Quantities
1. Length
- locate the position of a point in space
2. Mass
- measure of a quantity of matter
3. Time
- succession of events
4. Force
- a “push” or “pull” exerted by one body on
another
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
1.2 Fundamentals Concepts
Idealizations
1. Particles
- has a mass and size can be neglected
2. Rigid Body
- a combination of a large number of particles
3. Concentrated Force
- the effect of a loading
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
1.2 Fundamentals Concepts
Newton’s Three Laws of Motion
 First Law
“A particle originally at rest, or moving in a
straight line with constant velocity, will remain
in this state provided that the particle is not
subjected to an unbalanced force”
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
1.2 Fundamentals Concepts
Newton’s Three Laws of Motion
 Second Law
“A particle acted upon by an unbalanced force
F experiences an acceleration a that has the
same direction as the force and a magnitude
that is directly proportional to the force”
F  ma
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
1.2 Fundamentals Concepts
Newton’s Three Laws of Motion
 Third Law
“The mutual forces of action and reaction
between two particles are equal and, opposite
and collinear”
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
1.2 Fundamentals Concepts
Newton’s Law of Gravitational Attraction
F G
m1 m 2
r2
F = force of gravitation between two
particles
G = universal constant of gravitation
m1,m2 = mass of each of the two particles
r = distance between the two particles
Weight:
W G
mM e
r2
Letting g  GM e / r 2
yields W  mg
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
1.3 Units of Measurement
SI Units
 Stands for Système International d’Unités
 F = ma is maintained only if
– 3 of the units, called base units, are defined
– 4th unit is derived from the equation
 SI system specifies length in meters (m), time
in seconds (s) and mass in kilograms (kg)
 Force unit, Newton (N), is derived from F = ma
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
1.3 Units of Measurement
Name
Length
Time
Mass
Force
International
Systems of
Units (SI)
Meter
(m)
Second
(s)
Kilogram
(kg)
Newton
(N)
 kg .m 
 2 
 s 
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
1.3 Units of Measurement
 At the standard location,
g = 9.806 65 m/s2
 For calculations, we use
g = 9.81 m/s2
 Thus,
W = mg
(g = 9.81m/s2)
 Hence, a body of mass 1 kg has a weight of
9.81 N, a 2 kg body weighs 19.62 N
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
1.4 The International System of Units
Prefixes
 For a very large or small numerical quantity,
units can be modified by using a prefix
 Each represent a multiple or sub-multiple of a
unit
Eg: 4,000,000 N = 4000 kN (kilo-newton)
= 4 MN (mega- newton)
0.005m = 5 mm (milli-meter)
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
1.4 The International System of Units
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
1.5 Numerical Calculations
Dimensional Homogeneity
 Each term must be expressed in the same
units
 Regardless of how the equation is evaluated,
it maintains its dimensional homogeneity
 All terms can be replaced by a consistent set
of units
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
1.5 Numerical Calculations
Significant Figures
•
Accuracy of a number is specified by the
number of significant figures it contains
 A significant figure is any digit including zero
e.g. 5604 and 34.52 have four significant
numbers
 When numbers begin or end with zero, we
make use of prefixes to clarify the number of
significant figures
e.g. 400 as one significant figure would be 0.4(103)
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
1.5 Numerical Calculations
Rounding Off Numbers
 Accuracy obtained would never be better than
the accuracy of the problem data
 Calculators or computers involve more figures
in the answer than the number of significant
figures in the data
 Calculated results should always be “rounded
off” to an appropriate number of significant
figures
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
1.5 Numerical Calculations
Calculations
 Retain a greater number of digits for accuracy
 Work out computations so that numbers that
are approximately equal
 Round off final answers to three significant
figures
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
1.6 General Procedure for Analysis
 To solve problems, it is important to present
work in a logical and orderly way as
suggested:
1.
2.
3.
4.
5.
6.
Correlate actual physical situation with theory
Draw any diagrams and tabulate the problem
data
Apply principles in mathematics forms
Solve equations which are
dimensionally homogenous
Report the answer with significance figures
Technical judgment and common sense
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
Example
Convert to 2 km/h to m/s.
Solution
2 km  1000 m  1 h 
2 km/h 


  0.556 m/s
h  km  3600 s 
Remember to round off the final answer to three significant figures.
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at
ERT 146 Engineering Mechanics
Ms Siti Kamariah Md Sa’at