Welcome to

MMUP Engineers Registration Exam

Preparation Course

MECHANICAL

1
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 INTRODUCTION

Introduce yourself
➢ Name
➢ Education
➢ Experience
➢ Position

2
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 GROUND RULES
Mobile Silence
Interaction and participation in exercises
Questions are welcome
No side discussion
After about one hour and thirty minutes we can break

3
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 Course Content
1. Fluid Mechanics (Statics / Dynamics).
2. Pumps/ HVAC / Refrigeration. We have
3. Stress Analysis / Production / Materials. finished
4. NFPA codes / other General question.
5. Thermodynamics-1.
6. Thermodynamics-2.
7. Heat Transfer.
8. Compressors/Gas Turbine/Jet Engine.
9. Project Management Fundamentals-1.
10.Project Management Fundamentals-2.
4
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 First some fundamentals
Thermodynamics
UNDERSTANDING THE RELATIONSHIPS
BETWEEN
Pressure, Temperature, Volume ,Energy,
Work, Force, Power, Heat

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 STABLE VS. METASTABLE EQUILIBRIUM
 Stable equilibrium - System is at its lowest possible energy level.
 Metastable equilibrium - System is not at lowest possible energy.

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 Thermodynamics
Rub your hands together for 15 seconds.

Are your hands warm?

Thermal energy
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 Thermodynamics
The study of the effects of work, heat flow, and energy
on a system
Movement of thermal energy
Engineers use thermodynamics in systems ranging
from power plants, generators, desalination plants, to
electrical components.
SURROUNDINGS

SYSTEM

BOUNDARY
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 Thermal Energy versus Temperature
Thermal Energy is kinetic energy in transit from one object to another due to
temperature difference. (Joules)
Temperature is the average kinetic energy of particles in an object – not the
total amount of kinetic energy particles. (Degrees)

Temperature #1 Temperature #2

Heat
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 Temperature Scales
Scale Freezing point of Boiling point of
water water
Celsius 0°C 100°C
Fahrenheit 32°F 212°F
Kelvin 273K 373K
Matter is made up of molecules in motion (kinetic energy)
An increase in temperature increases motion
A decrease in temperature decreases motion
Absolute Zero occurs when all kinetic energy is removed from a object 0 K = -
273° C
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 Thermodynamic Equilibrium
Thermal equilibrium is obtained when touching objects within a system
reach the same temperature.
When thermal equilibrium is reached, the system loses its ability to do
work.
Zeroth Law of Thermodynamics: If two systems are separately found to
be in thermal equilibrium with a third system, the first two systems are
in thermal equilibrium with each other.
Object #1
(Thermometer)

Object #1 Object #2 Object #2 Object #3

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 Open, closed and isolated systems
 To a thermodynamic system two ‘things’ may be added/removed:
➢ energy (heat, work) ➢ matter.
 An open system is one to which you can add/remove matter (e.g. a open beaker to which we can add water).
When you add matter- you also end up adding heat (which is contained in that matter).
 A system to which you cannot add matter is called closed.
Though you cannot add/remove matter to a closed system, you can still add/remove heat (you can cool a
closed water bottle in fridge).
 A system to which neither matter nor heat can be added/removed is called isolated.
A closed vacuum ‘thermos’ flask can be considered as isolated.

Type of boundary Interactions Mass

Open All interactions possible (Mass, Work, Heat)
Closed Matter cannot enter or leave
Interactions possible
Semi-permeable Only certain species can enter or leave
Work
Insulated Heat cannot enter or leave
Rigid Mechanical work cannot be done*
Heat
Isolated No interactions are possible**
* By or on the system ** Mass, Heat or Work
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 Question 1
Which of the following variables controls the physical
properties of a perfect gas
(a) pressure
(b) temperature
(c) volume
(d) all of the above
(e) atomic mass.

Ans: d, all of the above

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 Question 2
Which of the following laws is applicable for the
behavior of a perfect gas
(a) Boyle's law
(b) Charles'law
(c) Gay-Lussac law
(d) all of the above
(e) Joule's law.

Ans: d, all of the above

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 1- Boyle's law
Boyle's law (sometimes referred to as the Boyle–Mariotte law, or
Mariotte's law[1]) is an experimental gas law that describes :
how the pressure of a gas tends to increase as the volume of the
container decreases. A modern statement of Boyle's law is
The absolute pressure exerted by a given mass of an ideal gas is
inversely proportional to the volume it occupies if the temperature
and amount of gas remain unchanged within a closed system.
Mathematically, Boyle's law can be stated as
P ∞ 1/V
PV = k
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 1- Boyle's law ( Cont.)

A graph of Boyle’s
original data A graph of Boyle's original data
This relationship between pressure and volume was first noted by Richard Towneley and

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 2- Charles' law
Charles' law (also known as the law of volumes) is an experimental gas
law that describes how gases tend to expand when heated. A modern
statement of Charles's law is:
When the pressure on a sample of a dry gas is held constant, the Kelvin
temperature and the volume will be directly related.[1]
This directly proportional relationship can be written as:

V∞T
 V /T = k
where:
V is the volume of the gas,
T is the temperature of the gas (measured in kelvins),
k is a constant.

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 2- Charles' law (Cont.)
 This law describes how a gas expands as the temperature
increases; conversely, a decrease in temperature will lead to a
decrease in volume. For comparing the same substance under
two different sets of conditions, the law can be written as:
 V1/T1 = V2/T2 or
 V1/V2 = T1 /T2 or
 V1 T2 = V2 T1
 The equation shows that, as absolute temperature increases, the
volume of the gas also increases in proportion

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 3- Gay-Lussac's gas law
 Gay-Lussac's gas law is a special case of the ideal gas
law where the volume of the gas is held constant.
When the volume is held constant, the pressure
exerted by a gas is directly proportional to the absolute
temperature of the gas.

 This example problem uses Gay-Lussac's law to find

the pressure of a heated container.
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 3- Gay-Lussac's Law Example 1:

Gay-Lussac's Law Example1:

A 20 L cylinder containing 6 atm of gas at 27 °C. What
would the pressure of the gas be if the gas was heated to
77 °C ?

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 3- Gay-Lussac's gas law (con.)
Solution:
The cylinder's volume remains unchanged while the gas is heated
so Gay-Lussac's gas law applies. Gay-Lussac's gas law can be expressed as

Pi/Ti = Pf/Tf
Where:

Pi and Ti are the initial pressure and absolute temperatures

Pf and Tf are the final pressure and absolute temperature

First, convert the temperatures to absolute temperatures.

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 3- Gay-Lussac's gas law (con.)
Ti = 27 °C = 27 + 273 K = 300 K
Tf = 77 °C = 77 + 273 K = 350 K

Use these values in Gay-Lussac's equation and solve for Pf.

Pf = PiTf/Ti
Pf = (6 atm)x(350K)/(300 K)
Pf = 7 atm
Answer:

The pressure will increase to 7 atm after heating the gas from 27 °C to 77 °C.
https://www.thoughtco.com/guy-lussacs-gas-law-example-607555
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 3- Gay-Lussac's gas law (con.)
Important Points About Gay-Lussac's Law
Volume and quantity of gas are held constant.
If temperature of the gas increases, pressure increases.
If temperature decreases, pressure decreases.
Temperature is a measure of the kinetic energy of gas molecules.
At a low temperature,
the molecules are moving more slowly and will hit the wall of a container less frequently.
As temperature increases,
the motion of the molecules are increasing. They strike the walls of the container more often, which is
seen as an increase in pressure.
The direct relationship only applies if temperature is given in Kelvin. The most common mistakes students
make working this type of problem is forgetting to convert to Kelvin or else doing the conversion incorrectly.
The other error is neglecting significant figures in the answer. Use the smallest number of significant figures
given in the problem.
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 Charles’ Gay Lussac's and Boyle’s Laws
Charles’ Law Gay Lussac’s Boyle’s Law
Law

P Constant T Constant
V Constant

V&T P&T PV = C

V1/T1 = V2/T2 P1/T1 = P2/T2 P1V1 = P2V2

V1/V2 = T1/T2 P1/P2 = T1/T2 P1/P2 = V2/V1

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 Question 3
The unit of temperature in S.I. units is
(a) Centigrade
(b) Celsius
(c) Fahrenheit
(d) Kelvin
(e) Rankine.

Ans: d , Kelvin
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 Question 4
The unit of mass in S.I. units is
(a) kilogram
(b) gram
(c) tone
(d) quintal
(e) newton.

Ans: a, kilogram
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 Question 5
The unit of time in S.I. units is
(a) second
(b) minute
(c) hour
(d) day
(e) year.

Ans: a, second
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 Question 6
The unit of length in S.I. units is
(a) meter
(b) centimeter
(c) kilometer
(d) millimeter.

Ans: a, meter

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 Question 7
The unit of energy in S.I. units is
(a) watt
(b)joule
(c)joule/s
(d)joule/m
(e)joule m..

Ans: b, joule
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 Question 8
According to Gay-Lussac law for a perfect gas, the absolute
pressure of given mass varies directly as
(a) temperature
(b) absolute
(c) absolute temperature, if volume is kept constant
(d) volume, if temperature is kept constant
(e) remains constant, if volume and temperature are kept constant.

Ans: c, absolute temperature, if volume is kept constant

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 Question 9
An ideal gas as compared to a real gas at very
high pressure occupies
(a) more volume
(b) less volume
(c) same volume
(d) unpredictable behavior
(e) no such correlation.

Ans: a >>>more volume

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 Question 10
General gas equation is
(a) PV=nRT
(b) PV=mRT
(d) PV = C
(c) PV=KiRT
(e) CpCv = Wj

Ans: b >> PV=mRT

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 Question 11
According to Dalton's law, the total pressure of the mixture
of gases is equal to
(a) greater of the partial pressures of all
(b) average of the partial pressures of all
(c) sum of the partial pressures of all
(d) sum of the partial pressures of all divided by average molecular weight
(e) atmospheric pressure.

Ans: c >> sum of the partial pressures of all

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 Dalton's law
 In chemistry and physics, Dalton's law (also called Dalton's law of
partial pressures) states that in a mixture of non-reacting gases, the
total pressure exerted is equal to the sum of the partial pressures of the
individual gases. ... and is relate

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 Question 12
Which of the following can be regarded as gas so that gas laws could be
applicable, within the commonly encountered temperature limits
(a) 02, N2, steam, C02
(b) Oz, N2, water vapour
(c) S02, NH3, C02, moisture
(d) 02, N2, H2, air
(e) steam vapours, H2, C02.

Ans: d >> 02, N2, H2, air

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 Question 13
The unit of pressure in S.I. units is
(a) kg/cm2
(b) mm of water column
(c) pascal
(d) dynes per square cm
(e) bars

Ans: c >> pascal

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 Question 14
A closed system is one in which
(a) mass does not cross boundaries of the system, though energy may
do so
(b) mass crosses the boundary but not the energy
(c) neither mass nor energy crosses the boundaries of the system
(d) both energy and mass cross the boundaries of the system
(e) thermodynamic reactions take place.

❖ Ans: a >> Mass does not cross boundaries of the system, though
energy may do so
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 Open Close and Isolated System

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 Open Close and Isolated System

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 Question 15
Temperature of a gas is produced due to
(a) its heating value
(b) kinetic energy of molecules
(c) repulsion of molecules
(d) attraction of molecules
(e) surface tension of molecules.

Ans: b >> kinetic energy of molecules

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 Question 16
According to kinetic theory of gases, the
absolute zero temperature is attained when
(a) volume of the gas is zero
(b) pressure of the gas is zero
(c) kinetic energy of the molecules is zero
(d) specific heat of gas is zero
(e) mass is zero.

Ans: c >> kinetic energy of the molecules is zero

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 Question 17
Kinetic theory of gases assumes that the
collisions between the molecules are
(a) perfectly elastic
b) perfectly inelastic
(c) partly elastic
(d) partly inelastic
(e) partly elastic and partly inelastic.

Ans: a >> perfectly elastic

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 Kinetic Theory

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What is the difference between an elastic and an inelastic collision?
 What is the difference between an elastic and an inelastic collision?
 A perfectly elastic collision is defined as one in which there is no
loss of kinetic energy in the collision. An inelastic collision is one in
which part of the kinetic energy is changed to some other form of
energy in the collision.
 The primary difference between, elastic and inelastic collisions
is:-
❖ in elastic collision, kinetic energy is conserved
❖ and in inelastic collisions, kinetic energy is not conserved.
❖ But in both elastic and inelastic collisions, momentum is
conserved.
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 Example of Elastic
 Are car accidents elastic or inelastic?
 Momentum is conserved, because the total momentum of
both objects before and after the collision is the same.
 However, kinetic energy is not conserved.
 Some of the kinetic energy is converted into sound, heat, and
deformation of the objects.
 A high speed car collision is an inelastic collision.

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 perfectly elastic collision
What is an example of a perfectly elastic collision?

Example:
 The collision between two billiard balls can be regarded as perfectly
elastic collision approximately.

 No energy is being radiated away (kinetic energy) or consumed

internally. Example : Bouncing of a ball when it hits the surface.

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 Elastic
What is the elastic collision? collision
 Elastic Collision: Collisions between objects are governed by laws
of momentum and energy. ... The total system kinetic energy before
the collision equals the total system kinetic energy after the
collision. If total kinetic energy is not conserved, then the collision is
referred to as an inelastic collision.

When the momentum is conserved?

 Conservation of momentum. So long as no external forces are acting
on the objects involved, the total momentum stays the same in
explosions and collisions. We say that momentum is conserved. You
can use this idea to work out the mass, velocity or momentum of an
object in an explosion or collision.
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 Kinetic Energy Lost

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 Elastic and Inelastic

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 Collision Elastic Example 1

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 Collision Elastic Example 1

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 Collision Elastic Example 2

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 Collision Elastic Example 2

 [0.25*4.5] + [0.3*(-5)] = [.25 *(-2)]+[0.3*V]

 [1.125] – 1.5 = [-0.5] + 0.3 V
 -0.375 = [-0.5] + 0.3 V
 -0.375 + 0.5 = 0.3 V
 0.125 = 0.3V
 V = – 0.125/0.3
 V= 0.417 m/sec

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 Question 18
The pressure 'of a gas in terms of its mean
kinetic energy per unit volume E is equal to
(a) E/3
(b) E/2
(c) 3E/4
(d) 2E/3
(e) 5E/4

Ans: d >> 2E/3

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 Molecular Constant

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 Question 19
An open system is one in which
(a)mass does not cross boundaries of the system, though energy may do
so
(b)neither mass nor energy crosses the boundaries of the system
(c)both energy and mass cross the boundaries of the system
(d)mass crosses the boundary but not the energy
(e)thermodynamic reactions do not occur.

Ans: (c) >> both energy and mass cross the boundaries of the
system
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 Question 20
Superheated vapor behaves
(a)exactly as gas
(b)as steam
(c)as ordinary vapor
(d)approximately as a gas
(e)as average of gas and vapor.

Ans: d >> approximately as a gas

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 Question 21
Absolute zero pressure will occur
(a) at sea level
(b) at the center of the earth
(c) when molecular momentum of the system becomes zero
(d) under vacuum conditions
(e) at a temperature of 273 °K

Ans: c >> when molecular momentum of the system becomes zero

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 Question 22
No liquid can exist as liquid at
(a) 273 °K
(b) vacuum
(c) zero pressure
(d) Centre of earth
(e) in space.

Ans: c >> zero pressure

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 Question 23
The unit of power in S.I. units is
(a) newton
(b) pascal
(c) erg
(d) watt
(e) joule

Ans: d >> watt

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 Question 24
The condition of perfect vacuum, i.e., absolute zero
pressure can be attained at
(a) a temperature of 273.16°C
(b) a temperature of 0°C
(c) a temperature of 273 °K
(d) a negative pressure and 0°C temperature
(e) can't be attained

Ans: a >> a temperature of 273.16°C

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 Question 25
Intensive property of a system is one whose value
(a) depends on the mass of the system, like volume
(b) does not depend on the mass of the system, like temperature, pressure,
etc.
(c) is not dependent on the path followed but on the state
(d) is dependent on the path followed and not on the state
(e) remains constant.

Ans: b >> does not depend on the mass of the system, like
temperature, pressure, etc.
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 Dalton's law
 In chemistry and physics, Dalton's law (also called Dalton's law of
partial pressures) states that in a mixture of non-reacting gases, the
total pressure exerted is equal to the sum of the partial pressures of the
individual gases. ... and is relate

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 General Gas Equation & Variable for gas

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 Constant [R]

1. The pressure must be in the unit

When using the Ideal Gas Law with 1 atm = 760 mmHg
atmospheres (atm)
the gas constant
R = 0.0821 L•atm/mol•K 2. The temperature must be in the
unit kelvin (K). T(K) = T(°C) + 273

3. The volume must be in the unit

liters

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 Molar Mass [M]

M : Molar Mass.
m : Mass of the gas
n : Moles

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 Example - 1
A gas at Standard Temperature
and Pressure (STP) has a PV = n RT
temperature of 273 K and a
P = 1.00 atm
pressure of 1.00 atm. What is the Require:
volume of 1.00 mole of gas at
STP? V=?
T = 273 K

n = 1 mole

R = 0.0821
L•atm/mol•K

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 Example - 2
A (0.120) g sample of CH4 gas W = 0.120 g
occupies a volume of 200. mL PV = n RT
at 35°C. What is the pressure of
the gas in mmHg ? Require: V = 200 mL

P = ? mmHg
T = 35 C

R = 0.0821
L•atm/mol•K

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 Kinetic Molecular Theory

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 Kinetic Molecular Theory

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 ➢ The root-mean-square speed measures the average speed of particles
in a gas, defined as.

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 Root-Mean-Square Speed Example

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