B-2 Physics Student Resource PDF

Student Resource Subject B-2: Physics Emirates Engineering Training Feb 2022 1  Emirates Engineering Training CONTENTS CONTENTS 3 DEFINITIONS...

Student Resource Subject B-2: Physics Emirates Engineering Training Feb 2022 1  Emirates Engineering Training CONTENTS CONTENTS 3 DEFINITIONS 5 STUDY RESOURCES 6 INTRODUCTION 7 Topics: 2.0 What is Physics? 2.1 Matter 2.2.1 Statics 2.2.2 Kinetics 2.2.3 Dynamics 2.2.4 Fluid Dynamics 2.3 Thermodynamics 2.4 Optics (Light) 2.5 Wave Motion and Sound Feb 2022 2 Emirates Engineering Training This Page Intentionally Left Blank Feb 2022 3  Emirates Engineering Training DEFINITIONS Define To describe the nature or basic qualities of. To state the precise meaning of (a word or sense of a word). State Specify in words or writing. To set forth in words; declare. Identify To establish the identity of. List Itemise. Describe Represent in words enabling hearer or reader to form an idea of an object or process. To tell the facts, details, or particulars of something verbally or in writing. Explain Make known in detail. Offer reason for cause and effect. Feb 2022 4  Emirates Engineering Training STUDY RESOURCES B-2 Physics Student Resource Feb 2022 5  Emirates Engineering Training INTRODUCTION On completion of the following topics you will be able to: Topic 2.0 What is Physics The Universe Energy Matter Density Time Motion Energy and Force Pressure Electricity Order of Magnitude Ambient Conditions Ambient Temperature International Standard Atmosphere Topic 2.1 Matter Define the nature of matter regarding: The chemical elements Structure of atoms Molecules. Define chemical compounds. Define matter in solid, liquid, and gaseous states. Identify changes between states of matter and define the process. Topic 2.2.1 Statics Describe forces, moments and couples and represent the interaction of these as a vector describing simple machines and mechanical advantage. Describe the centre-of-gravity of a mass. Describe the elements of theory of stress, strain and elasticity to the following: Tension Compression Shear Torsion. Describe the nature and properties of solids, fluids, and gases. Describe the action of pressure and buoyancy in liquids (barometers). Topic 2.2.2 Kinetics Describe the following aspects of linear movement: Uniform motion in a straight line Vibration Harmonics Resonance. Feb 2022 6  Emirates Engineering Training Describe velocity ratio, mechanical advantage and efficiency. Topic 2.2.3 Dynamics Describe the following with regard to mass: Mass Force Inertia Work Power Energy (potential, kinetic and total) Resultant force and equilibrium Heat Efficiency. Describe momentum and conservation of momentum. Describe impulse. Describe gyroscopic principles. Describe friction, its nature and effects, and the coefficient of friction (rolling resistance). Topic 2.2.4 Fluid Dynamics Describe specific gravity and density in relationship to fluids Describe the following in relationship to fluids: Viscosity - fluid resistance Effects of streamlining Effects of compressibility Describe the following types of pressure: Static Dynamic Total State Bernoulli’s Theorem and describe the operation of a venturi. Topic 2.3 Thermodynamics Describe temperature and the operation of thermometers. Describe the following temperature scales: Celsius Fahrenheit Kelvin. Define Heat Define specific heat and describe heat capacity Describe the following methods of heat transfer: Convection Radiation Conduction Describe volumetric expansion. State the first and second laws of thermodynamics Describe the following regarding gases: Ideal gas laws Constant volume and constant pressure Refrigerators and heat pumps Latent heats of fusion and evaporation Feb 2022 7  Emirates Engineering Training Thermal energy Heat of combustion Topic 2.4 Optics (Light) Describe the nature of light and state the speed of light Describe the laws of reflection and refraction: Reflection at plane surfaces Reflection by spherical surfaces Refraction of light through various media The use of lenses Describe the nature and use of fibre optics. Topic 2.5 Wave Motion And Sound Describe the nature of wave motion: Mechanical waves Sinusoidal wave motion Interference phenomena Describe the characteristics of sound: Production Intensity Pitch Quality State the speed of sound and describe factors that affect it Describe the Doppler Effect. Feb 2022 8  Emirates Engineering Training Table of Contents WHAT IS PHYSICS?..........................................................................................................................................2 Origins of the Universe...................................................................................................................................3 Nature of the Universe...................................................................................................................................4 What is energy?..............................................................................................................................................4 What is matter?..............................................................................................................................................4 Properties of Matter......................................................................................................................................4 Density............................................................................................................................................................5 Time................................................................................................................................................................5 Motion............................................................................................................................................................5 Energy and Force............................................................................................................................................6 Pressure..........................................................................................................................................................6 Initial Conclusions...........................................................................................................................................7 P.S. What about Electricity?...........................................................................................................................7 Order of Magnitude........................................................................................................................................8 Ambient Conditions........................................................................................................................................9 Ambient Temperature....................................................................................................................................9 International Standard Atmosphere..............................................................................................................9 Feb 2022 9  Emirates Engineering Training WHAT IS PHYSICS? Ever since Humankind developed the ability to ponder its existence, questions have been asked concerning the nature of its environment. Latin, the language of the Roman Empire, contained the word ‘Physica’ for ‘Nature’, hence our use of ‘Physics’ as the overall name of the body of knowledge which attempts to describe the inanimate world. We have become adept at observing and measuring the phenomena that surround us. Certain individuals, e.g. Archimedes and Newton, through chance and circumstance, were able to develop the relationships, between elements of these events, which are now called the Laws of Physics. In many cases, the absolute truths still elude us, and the scientific community has only ‘models’ to offer; for example, the origin of the Universe, or the structure of the atom. Even so, we have now gained enough knowledge to create and control the technological environment in which we live. This course attempts to address the basics which serve to underpin most of the technical knowledge that an Aircraft Maintenance Engineer needs. For organisational purposes, Physics is divided up into a number of topics, however it is important to remember that nature works its various strands of magic simultaneously. The rest of this introduction endeavours to provide the reader with the absolute minimum of knowledge with which to attack these separate topics. physic thatfocus on matter and of science is a branch motion well astheir as energy Feb 2022 10  Emirates Engineering Training Origins of the Universe Recent observations have given us the “Big Bang Theory”, which in its most basic form, tells us that the space in which you and I, and the rest of the 1050 kg of matter exist, began as a point source, and has expanded into what we call the Universe. The universe has clumped together into Galaxies, and within these are Planetary Systems associated with Stars. The most frequently asked question when faced with this concept is: “OK, what was there before the Big Bang?” Well, the simplest answer is “nothing” because time itself came into existence and there is can be no concept of “before.” See Fig 1. There are no time values for any universe size less than zero. stars vs planets Big Bang theory madeofhydrogen can be made helium and ofrock Ice an explosion and 1 startsfrom itformedstarsand planets usually in plasmastate gas or water down 2 aftercooling have formed been Doesn't have to must Be orbiting solarsystem star 3 then a orbiting anything a be galaxies 4 lastly Don't Emitlight Extra notes emits Light gravity ofthereown stars have extremehigh tothe sun colderthan close hottestobjectin its Always because they are itstars system depends on mass 1 gravity Fusion No Fusion fots hydrogen has of form helium For all intents and purposes, our concept of time asto a means by which we can measure the rate at which events occur will suffice, and our studies will concentrate on those topics which explain our everyday lives. Feb 2022 11  Emirates Engineering Training component main splitsintotwo matter ti energy Nature of the Universe Apart from its size, what are the other characteristics or properties of the Universe as we perceive it today? What does it contain? We have already mentioned one - the 1050 kg of matter. The other is energy. needenergy inorder f tw What is energy? you I toapplywork nyh The Greek word, “energos” - means “that by which activity is possible”, so in non- physics terms, it could be thought of as “that which causes change”. However, that is not measurable enough for physicists. internal s energybut used We say that energy provides the “capability to change the state of motion, or matter” of some object or not be other, and exists in many forms in a fixed amount. For example, kinetic energy is the energy possessed by a anytime moving mass capable of causing change, while potential energy is the energy within a compressed spring which could cause change. Energy used is always fully accounted for in terms of the activity produced. What is matter? tiene neither Effi g The states of matter can be solid, liquid or gaseous, and each of these is related to the amount of internal energy possessed by the matter being under consideration. We can detect this internal energy, and call it heat. It was originally thought to be an invisible fluid called caloric; however, we now know it is bound up in the vibratory motion of the basic particles which make up matter, called atoms and molecules. movementofenergy The amount of heat present depends on the quantity of matter, but how hot it is doesn’t. We express “hotness” as “temperature” and it is measured in degrees. Our star, called the Sun, has radiated energy on to this planet all through its existence, and all changes of state or motion we experience today, are only possible because of this radiation, past and present. An exception to this is the development and use of Atomic or Nuclear Energy, which involves the conversion of matter into energy, in a similar way to that process used by stars. Properties of Matter anythinghasmegsandvoly.me Amounts of matter are measured in units of mass of which the standard is the kilogram, and the presence of a mass affects space in two ways. Firstly, there is the amount of space occupied by a certain mass. This is represented by its size in three dimensions. The product of an object’s length, width, and height is called volume, and when all three dimensions are measured in metres, we get cubic metres. surrounding it. Feb 2022 12  HEAT What is heat? It was originally thought to be an invisible fluid called caloric. However it is now observed as the “internal energy” of matter. You will learn that all matter is composed of fundamental particles called atoms or molecules. These particles are in constant vibratory activity and therefore posses energy. We detect and measure this energy, and call it heat. The degree of hotness is called a body’s temperature. BUSINESS DOCUMENT This document is intended for business use and should be distributed to intended recipients only. Feb 2023 ☻ Slide No. 5  GRAVITY Hiiiii The presence of a mass in space somehow affects that space, so that two or more masses attract each other. Gravity exists as a “field”. W One thing that the force of attraction depends on, is the relative size of the masses involved. For us, the planet is immense, and so dominant, that we are continuously attracted to it. Should we be unsupported by the ground or a floor, we fall toward the centre of the Earth. We measure this force of attraction and call it weight. If you took a lump of matter to the moon, (the moons mass is 1/6 that of earth), the lump’s weight would also be 1/6 smaller than it would be if it was on earth. BUSINESS DOCUMENT This document is intended for business use and should be distributed to intended recipients only. Feb 2023 ☻ Slide No. 7  Emirates Engineering Training pensityitsmassf.name andvolume are inversely Density Density toeachother proportional To compare different types of matter, let us see how much of each occupies each cubic metre of space, i.e. the number of kilograms of the substance per cubic metre. This derived property thus measures the density of a particular substance, and we get the first relationship between properties, i.e. our first Law of Physics: rho f of symbol As mentioned, the unit’s kilogram and metre are standardised, and most countries maintain an organisation to ensure that they represent the same measurement at all times. In Australia, this is the National Measurement Laboratory, located within the CSIRO Division of Applied Physics in Sydney. The unit kg/m3 is a derived unit. Time is the 4thdimension The measurement of space occupies three dimensions of the Universe, but is not sufficient for us to include the progress of an event in that measurement. For this we have the concept of time, often called the Fourth Dimension. Our ancestors observed the cycles of nature, the passage of the sun etc. which gave them the initial units of days and years. The basic unit of time, the second, s is now fundamental and standardised. Motion With the concept of time, we can measure how a mass may change its position in space, in other words, the idea of motion. An object, (a mass), can be in particular state of motion: velocity At rest (not moving), zero metres per second, (0 m/s). speed or Changing its position at a constant rate, (i.e. a certain number of metres per second). accelerate Or, that rate could itself be changing with time, giving us metres per second per second, (m/s2). A constant rate of metres per second (m/s) is called speed or velocity A constant rate of metres per second per second (m/s2) is called acceleration What is required to be able to change this State of motion? Feb 2022 13  ACCELERATION For objects to start and stop there must changes in speed with time. This is called acceleration and is measured in metres per second per second (m/s2) What causes motion? Application of force. Force is that which produces a change of motion state, (push or pull through contact) or the action of a field. Isaac Newton defined force as the product of mass times the acceleration produced. 1 Newton of force will accelerate 1 kg of mass by 1 metre per second per second. BUSINESS DOCUMENT This document is intended for business use and should be distributed to intended recipients only. Feb 2023 ☻ Slide No. 10  TYPES OF PUSH AND PULL A different type of push or pull exists, capable of changing motion states, exerted by a field of force. They exert their influence through space without contact. Examples are: magnetism gravity electrical Pressure is defined as the force exerted over an area. Typical units are N/m2 or pounds per square inch (psi). BUSINESS DOCUMENT This document is intended for business use and should be distributed to intended recipients only. Feb 2023 ☻ Slide No. 11  Emirates Engineering Training piratiestoned pushoraput my p a Energy and Force English scientist, Isaac Newton (1642 – 1727), observed that if you gave a mass a push or a pull, its state of motion changed. For example, just going from “at rest” to “moving” meant acceleration must have taken place. Energy has been used in this process, but not used up. The energy used to propel the object still exists as the object’s motion, (and in other forms that will be discussed later). The energy required to provide the push to change this state of motion was found to depend on the mass contained in the object and the amount of acceleration. More mass and/or more acceleration required more push. To quantify this push or pull, Newton took the product of the mass and acceleration required, and called it force, - that which is required to change motion state. N kg m1s This will give us another derived unit for force, the kg.m/s per s, which is far too unwieldy, so appropriately enough 1 kg.m/s per s, is actually called 1 Newton. Forces are not always applied by direct contact with an object. Let us revisit gravity. Should you be unlucky enough to be unsupported by the ground or a floor in the Earth’s gravitation field, you will experience a change in motion state. (Fall !). Ignoring for the moment that we have an atmosphere which actually slows thing up a bit, it can be shown that we fall with an acceleration of 9.8 m/s per s. This is called the “acceleration due to gravity” for Earth, and has its own symbol - “g”. g 9.8m s From above, Force = Mass x Acceleration, and when that acceleration is “g”, that force is called your weight. F mg its weight W To all intents and purposes, g is constant for all us Earth bound surface dwellers, so interchanging the words mass and weight does not lead to short measures! (After Blaise Pascal (1623 - 1662)). Feb 2022 14  Emirates Engineering Training sweetie L Work and Power Energy was used during our application of force, and to help quantify what happens to this energy, we take the product of the applied force and the distance moved during the change of position, and we call it work. Work = Force x Distance moved The work done equals the energy used, including the energy used to overcome any resistance, e.g. friction and air resistance. Another derived unit appears, the Newton Metre, better known as the Joule after James Joule (1818 -1889), and can now be used as the standard unit for energy of any form. Power is simply a measurement of the rate at which work is done or energy is used. as watts known = / Joules per second are called Watts, after James Watt (1736 – 1819), who experimented with the work done by horses as they pulled barges around the canals of England. 1 horsepower 746 W 1horspowr 746 Initial Conclusions So, what is physics? The study of matter and the activity it gets up to with the energy available? In its simplest form, the Universe can be said to be a collection of Matter and Energy, so that may be as good an answer as any, but to be sure we must now start investigating things further by in the more traditional manner topic by topic. Initially, we will take a closer look at the structure of matter, both in its everyday and smallest form. Then there will be more on how force can be put to good use and how different types of motion can be analysed. Different forms of energy are discussed, including Heat, Light, and Sound, to see how they create the various phenomena that occur. The relationships between the Matter and Energy could just as easily be called the Laws of Nature. Add Chance to the mix and maybe, just maybe, the picture is complete. P.S. What about Electricity? will be briefly introduced when we look at the structure of matter in its smallest forms (atoms and molecules). Feb 2022 15  Emirates Engineering Training Fundamental Units The System Internationale, (SI or Metric System) has been internationally agreed, but there are many examples of the British System still used, for example, psi for pressure. PROPERTY METRIC (SI) BRITISH CONVERSION MASS KILOGRAM KG SLUG 1 SLUG = 14.59 KG LENGTH METRE M FOOT FT 1 FT = 0.305 M TIME SECOND SECOND N/A FORCE NEWTON N POUND LB 1 LB = 4.45 N PRESSURE PASCAL PA LB/SQ IN (PSI) 1 PA = 0.00015 PSI WORK/ENERGY JOULE FOOT POUND 1 J = 0.738 FT.LB ACCELERATION 9.81 M/S PER S 32.2 FT/S PER S N/A DUE TO GRAVITY Order of Magnitude In the metric system, many prefixes are used to denote how many of any particular unit are being used. The following table will be useful. Feb 2022 16  Emirates Engineering Training Ambient Conditions Atmospheric Pressure We live at the bottom of an atmosphere comprising of a mixture of gaseous elements and compounds called air. The weight of air acts over the surface of the planet causing it to be ‘under atmospheric pressure’, according to the rule P = F/A. N m is same as pa Extending to 160,000 km, with a varying density depending on height, one atmosphere exerts an average pressure, at sea level of 101,320 N/m2 ; i.e. 101,320 Pa, which is more commonly written as 1013.2 hPa (hectopascals). Alternatively, 1 bar = 100,000 Pa, so I atmosphere is 1.0132 bar or 1013.2 mb. In British units, 1 atmosphere is 14.7 lb/in2. taoneusehisu.ae PSI same as Ib in poundperinchsquare One practical method of determining atmospheric pressure is to measure how high a column of liquid can be supported by this pressure. (A barometer). It turns out to be 29.92 inches or 760 mm of mercury. We feel no ill effect from this pressure because we are permeable enough to allow the pressure inside us to equalise to this. Rapid ascents or descents through the atmosphere are a different story, and aircraft are engineered to cope with this. Ambient Temperature isactually taste The sun radiates its energy continuously on the planet and its atmosphere. Over time, this ocean of air has settled into a complex series of weather patterns, one element of which is the temperature at any given location. This changes from place to place, and with your height above sea level. The temperature is measuring the relative degree of hotness of one area over another and is constantly changing as the day proceeds and the weather patterns shift. At sea level, the temperature ranges from about -30 “degrees Celsius” to about +50°C. At the typical cruising height of a passenger jet, the temperature is just above -60°C. International Standard Atmosphere The performance of any aircraft depends heavily on air density, and we’ve just seen that density varies from location to location and with height, as the atmospheric pressure changes with the time of day and weather experienced. To create a benchmark against which aircraft performance can be measured, an International Standard Atmosphere (ISA) was defined. The essential features of the ISA are a sea level temperature of 15°C, and pressure equal to 1013.2 hPa. heetopas.de teeto 18 Should the conditions be different from these at a particular location, then important performance factors standard we are using whenever experiment so use values 1013.2hPa p 5 152 and Feb 2022 17 Emirates Engineering Training This page intentionally blank Feb 2022 18  Emirates Engineering Training Table of Contents TOPIC 2.1: MATTER........................................................................................................................................2 Elements.........................................................................................................................................................3 The Periodic Table of Elements......................................................................................................................4 Ions.................................................................................................................................................................4 Isotopes..........................................................................................................................................................4 Compounds....................................................................................................................................................5 Molecules.......................................................................................................................................................6 Mixtures.........................................................................................................................................................6 States of Matter..............................................................................................................................................7 Solids..............................................................................................................................................................7 Liquids............................................................................................................................................................8 Gases..............................................................................................................................................................8 Flow................................................................................................................................................................8 Feb 2022 19  Emirates Engineering Training TOPIC 2.1: MATTER Matter refers to everything which occupies space, and has mass which exists in one of three physical states, solid, liquid and gaseous. The total mass of the Universe is conserved; this meaning it cannot be created or destroyed, only changed from one form to another. If you burn 1kg of wood, you finish with 1 kg of ash, smoke, and other gases. Before we can discuss the different properties of each state, let us look at how all forms of matter are put together. Matter itself is made up of small particles. The simplest forms of matter are the elements, whose constituent particles are called atoms, as modelled below (Fig 1). Atoms are largely space with a relatively dense nucleus made up of elementary particles, protons and neutrons, and one or more shells of electrons at certain fixed distances. Each shell represents an energy level within the atom. It requires some two hundred million of them side by side to form a line a centimetre long. Imagine the full stop at the end of this sentence. It is probably about 0.5 mm in diameter. If that represents the nucleus, then the electrons in the first shell would be about 50 metres away. Figure 1 Carbon atom and oxygen atom Within the atom, there are four Fundamental Interactions which give rise to all other physical processes in the Universe. Simply described, and in order of increasing strength, they are: 4. The Strong Nuclear Interaction; holds the nuclei together. Feb 2022 20  Emirates Engineering Training To help analyse interaction 3, we say the proton has a positive electric charge, and the electron, a negative electric charge, where charge is a fundamental property of matter at this level, (in a similar way to mass at all levels.) (The words ‘electron’ and ‘electricity’ come from the Greek word for ‘amber’, the first substance investigated with some of the properties we now control so confidently today). Elements Elements are detailed in the Periodic Table. For example, pure copper (Fig 2) is an element because it is comprised only of copper atoms (Cu). An atom is the smallest part of an element that retains the properties of that element. f iii a Figure 2 Copper atom Electrons surround the nucleus in successive groups or shells – like spheres within spheres. A Copper atom has 2 electrons in its first or K shell, 8 in the second or L shell, and 18 in the third or M shell, and one electron in its fourth (N) and final, outer shell. Whether the outer shell is relatively empty, half full, or nearly full determines some of the electrical properties of the element. All atoms follow this rule: Feb 2022 21  Emirates Engineering Training The Periodic Table of Elements Each atom has an identifiable number of protons, neutrons, and electrons. In addition, every atom has its own atomic number, as well as its own atomic mass (as depicted in the periodic table below (Fig 3). Figure 3: The Periodic Table of Elements Copper has an Atomic Number of 29, because it has 29 protons. Its Atomic Mass is amu, a more complex calculation involving averaging the mass of the total number of protons and neutrons together. (Electron mass is 0.0005 times less than either a proton or a neutron, and considered insignificant). Ions Ions are atoms which have lost or gained an electron during a process. An atom losing an electron will become positive, whilst an atom gaining an electron will become negative. Isotopes Isotopes are atoms of the same element with different numbers of neutrons. The Atomic Number remains the same, but the Atomic Mass changes. Feb 2022 22  Emirates Engineering Training compound smfhmolecule a Compounds is There are 109 known elements currently, however most of the matter around us has been formed by one or more elements combining in such a way to form completely new substances called compounds. This is called chemical bonding, and generally when atoms bond together, they share or transfer electrons and form molecules. Water is a compound because it is made up of hydrogen and oxygen atoms (H2O). The same is true of carbon dioxide (CO2) and common salt, sodium chloride (NaCl). In the example of H2O, water, (Fig 4) the oxygen atom has six electrons in its outer, or valence shell. Because there is room for eight electrons in the valence shell, one oxygen atom can combine with two hydrogen atoms by sharing the single electron from each hydrogen atom. Figure 4: Water molecule A compound is matter in which all the molecules are identical, but the molecules are comprised of different atoms in exact proportions. The two or more individual elements are chemically combined to form a separate substance whose characteristics may be completely different from the original element characteristics. Feb 2022 23  Emirates Engineering Training they stablething their 18 molecule are servicealone by chinment can in the group Molecules own gasesare for A molecule can have: noble all Just one atom (helium) Two atoms of the same element (oxygen – O2) Atoms of several different elements (water – H2O) Subscripts indicate number of particular atoms in the molecule Al2 O3 means two atoms of aluminium and three atoms of oxygen in each molecule of alumina. form is alloymixture Figure 5: Alumina molecule Mixtures of A mixture is a mingled mass of two or more substances where each substance retains its own individual characteristics. For example, figure 6 below is a representation of NaCl in H2O (salty water). Mixtures have varying ratios of ingredients that do not combine chemically as they do in a compound. metal alloys. Metal alloys sometimes change characteristics when the metals are merged. For example, aluminium Feb 2022 24  water and corner Emirates Engineering Training when sugar arsenixestigar butsee can we becomes stronger and harder when alloyed with certain other metals. This is a physical rather than a chemical combination, occurring at a microscopic scale. Figure 7 is a microscopic cross-section of a metal alloy showing crystalline structure. Mixtures may be separated into the original substances. is known as alloy combined twometalstogether wheneveryou Fe C steel Example Earbon ion at mixture steelis an alley the change does not state state chemical physical Figure 7 Crystalline structure of metal alloy States of Matter All atoms and molecules in matter are constantly in vibratory motion. The degree of motion i.e. the internal kinetic energy possessed by the matter, determines its physical state. This internal KE is what we know as e this molecular activity. heat. What we call ‘temperature’ is, in fact, only a measure of So, at the everyday scale of things, these elements, compounds and mixtures exist as solids liquids or gases, depending on their internal energy or heat content. The physical state of a compound has no effect on a compound’s chemical structure. Ice, water, and steam are all H2O. (Fig 8). Liquid gas it Pressurize down cool it IEEE Solids iimission Figure 8 The three states of matter tiITmeTtuid gs Feb 2022 25  Emirates Engineering Training Liquids When heat energy is added to solid matter its molecular movement increases. This causes the molecules to overcome their rigid shape. When a material changes from a solid to a liquid, the material’s volume does not significantly change. However, the material conforms to the shape of the container it’s held in. Liquids have definite volume but not shape. An example of this is molten steel. Although the molecules of a liquid are farther apart than those of a solid, they are still not far enough apart to make compressing possible and liquids are also considered incompressible. In a liquid, the molecules still partially bond together. This bonding force is known as surface tension and prevents liquids from expanding and spreading out in all directions. Surface tension is evident when a container is filled. Gases As heat energy is continually added to a material, the molecular movement increases further until the liquid reaches a point where surface tension can no longer hold the molecules down. At this point the molecules escape, becoming gas or vapour. The amount of heat required to change a liquid to a gas varies with different liquids. Gases differ from solids and liquids in the fact that they have neither a definite shape nor volume. Chemically, the molecules in a gas are exactly the same as they were in their solid or liquid state. However, because the molecules in a gas are spread out, gasses are compressible. Flow The same property that allows liquids and gases to adopt the shape of their containers, also allows them to flow, and they can both be called fluids. liquid gas andbothcan because flow Feb 2022 26  Emirates Engineering Training TOPIC 2.2: MECHANICS Table of Contents TOPIC 2.2: MECHANICS......................................................................................................................................1 TOPIC 2.2.1: STATICS......................................................................................................................................3 FORCES............................................................................................................................................................3 Moments and Levers......................................................................................................................................5 First-Class Lever..............................................................................................................................................5 Second-Class Lever.........................................................................................................................................6 Third-Class Lever............................................................................................................................................6 Velocity Ratio.................................................................................................................................................7 Couples...........................................................................................................................................................7 Centre of Gravity (CG).....................................................................................................................................8 Balance of Rotating Components.................................................................................................................10 Stress............................................................................................................................................................11 Strain............................................................................................................................................................11 Tension.........................................................................................................................................................12 Compression.................................................................................................................................................12 Shear Stress..................................................................................................................................................13 Torsional Stress.............................................................................................................................................14 Pressure........................................................................................................................................................14 Pressure in Fluids..........................................................................................................................................15 Density and Specific Gravity.........................................................................................................................15 Buoyancy......................................................................................................................................................16 Pressure........................................................................................................................................................17 Measurement of Pressure............................................................................................................................18 Properties of Solids, Liquids and Gases........................................................................................................19 TOPIC 2.2.2 - KINETICS..................................................................................................................................20 DISPLACEMENT AND DISTANCE....................................................................................................................20 SPEED AND VELOCITY...................................................................................................................................21 PERIODIC MOTION........................................................................................................................................26 Pendulum.....................................................................................................................................................27 Feb 2022 27 Emirates Engineering Training Mass on a spring...........................................................................................................................................27 RESONANCE..................................................................................................................................................29 Harmonics....................................................................................................................................................29 Topic 2.2.3 – DYNAMICS...............................................................................................................................30 The difference between mass and weight....................................................................................................30 INERTIA.........................................................................................................................................................31 WORK............................................................................................................................................................31 POWER.........................................................................................................................................................32 Activity......................................................................................................................................................32 ENERGY.........................................................................................................................................................32 Potential Energy............................................................................................................................................33 Kinetic Energy...............................................................................................................................................33 Total Energy..................................................................................................................................................34 FRICTION......................................................................................................................................................34 HEAT.............................................................................................................................................................37 EFFICIENCY...................................................................................................................................................38 MOMENTUM................................................................................................................................................39 A SIMPLE GYROSCOPE..................................................................................................................................40 IMPULSE.......................................................................................................................................................41 Topic 2.2.4 – FLUID DYNAMICS....................................................................................................................42 PHYSICAL NATURE OF MATTER.....................................................................................................................42 DENSITY........................................................................................................................................................43 SPECIFIC GRAVITY (S.G.)................................................................................................................................44 VISCOSITY IN LIQUIDS...................................................................................................................................45 VISCOSITY IN GASES......................................................................................................................................46 VISCOSITY INDEX..........................................................................................................................................46 STREAMLINING.............................................................................................................................................47 COMPRESSIBILITY.........................................................................................................................................47 EFFECTS OF COMPRESSIBILITY.....................................................................................................................48 STATIC, DYNAMIC AND TOTAL PRESSURE....................................................................................................49 Measuring Dynamic Pressure.......................................................................................................................51 Feb 2022 28  Emirates Engineering Training definition of force TOPIC 2.2.1: STATICS FORCES A force can be described as that which can produce a change in a body’s state of motion. An application of force will: Start Stop Accelerate, or Decelerate, a mass If energy is available, then forces can be used to do work. Force is an example of a vector quantity that needs magnitude (size) and direction to be fully defined (Fig 1). Figure 1 A vector has magnitude and direction Most quantities are scalars and are defined with size only, for example, temperature, length, and time. Scale drawings are a convenient way to represent vectors (Fig 2). Feb 2022 29  Emirates Engineering Training Ñ w FISH t A 11 knows Figure 2 Vector addition Sometimes, forces act at different directions on a body. In cases such as these, forces must be resolved to calculate a resultant net force. Note direction balanced object samemagnitudeand direction opposite magnitude same equilibriumobject y and horizontal components Figure 3 Lift is the resultant force of the vertical When an object does not change its state of motion or rest, the resultant of all the forces acting on it is zero, and it is said to be in a state of equilibrium. hementaltone mhts a sin EII.fi Feb 2022 30  scalar Emirates Engineering Training vector w t distance M F turningforce York force moment Icedistance gMoments and Levers Either side of the lever below (Fig 4) has a moment which is the force multiplied by the distance, from the fulcrum, or pivot, (called the arm). Figure 4 Simple lever The system is balanced when the load moment and the effort moment are equal. If the effort force is increased, the load will be raised. The smaller effort force moves through a larger arc to raise the heavier load a small distance. load moreeffort more This is the principle behind “leverage”. A lever is an example of a Simple Machine, which is a device used to gain a Mechanical Advantage( MA), In other words, the multiplication of a force by the use of leverage. The mechanical advantage of a first-class lever depends on the distance moved by effort compared to load. First-Class Lever MA greaterthan 1 Fulcum in middle load is greaterthaneffort The purpose of a lever is to perform work, for a load (L) to be lifted by an effort (E), pivoting around a fulcrum (F). If the load moved is greater than the effort used, the machine has an MA greater than 1. A crowbar is an example of a first-class lever. In Figure 5, the fulcrum is situated between the load and the effort, and the load is greater than the effort. The load only needs to be raised a short distance but effort travels a larger distance, hence “leverage”. Figure 5 First class lever Feb 2022 31  Emirates Engineering Training in middle loadgreaterthan Second-Class Lever MA greaterthan 1 load effort Examples of a second-class lever (Fig 6) include cockpit control levers, such as a throttle or thrust lever, and a simple wheelbarrow. The load is situated between the fulcrum and the effort. The load is greater than the effort = Positive MA. Figure 6 Second-class lever 1 in middle load less than effort Third-Class Lever MA lessthan Effort The effort is between the fulcrum and the load (Fig 7). The effort is greater than the load, and moves through a smaller distance MA is less than 1. An example of a third-class lever is the retraction mechanism on an aircraft landing gear. Figure 7 Third-class lever A Equations MA 444ft Effort Am Load load Am Effort Feb 2022 32  Emirates Engineering Training Velocity Ratio A Velocity Ratio is the direct ratio of two speeds that may be present in the same system. For example, consider a pulley system that uses a Mechanical Advantage of 4. The operator will pull through a metre of rope to raise the load by 0.25m. Therefore, the rope moves 4 times as fast as the load is being raised. (Fig 8). The velocity ratio is 4:1. So, MA = Distance Ratio = VR. MA of pulley system numbers is equal to the thesystem in ofropepresent ropethat Except theupper downward 8 that is actting 4 In this figureMA will To times velocity ratio a MA 1 yaways move as 1 faster number being of rom is Figure 8 Pulley system Couples A couple is a type of moment which is derived from two equal forces acting in parallel but opposite directions on two different points of a body. To explain this concept, consider an aircraft flying straight and level. If a control input is made to turn the aircraft to the left, a force is generated at both the left wing tip and the right wing tip through the ailerons (Fig 9). FE'j couples F and Fz are Beloon Feb 2022 33  Emirates Engineering Training Figure 9 The roll forces are equal, but act in opposite direction The forces produce a torque or twisting force to the aircraft, causing it to turn. If the wing span of the aircraft is b metres, then the torque produced by this couple is given by: EG distance T = F x b Nm torque Other examples include taps and steering wheels. cgrelatedtnomig hate 7wphhsent.mt Centre of Gravity (CG) cg The Centre of Gravity (‘CG’ or ‘C of G’) of a body is the point from where the weight appears to act, irrespective of the body’s position. The CG of regularly shaped bodies of uniform density is easy to find. It is simply the geometric centre of the bodies (Fig 10). by an upward-acting force applied to the underside of the body where the vertical exactly leaves it. Application of the upward force at any other point would tend to tilt the body. Therefore sling or lift loads as near to the CG as possible. Feb 2022 34  Emirates Engineering Training whitorott in pages diets Figure 11 CG is the intersection of the verticals am The centre of gravity of an aircraft shifts if passengers, baggage, or equipment in the cabin move, or if unequal amounts of fuel are used from tanks in opposite wings. There is a range of acceptable CG positions between a forward limit and an aft limit. This will ensure the aircraft remains controllable without becoming tail heavy or nose heavy (Fig 12). further to this, balance will be retained regardless of the number of weights that are added to the disc, providing they are paired off diametrically with equal and opposite moments. Feb 2022 35  Emirates Engineering Training Balance of Rotating Components Even with an object of regular shape—a disc or wheel for instance—the thickness or other dimensions may vary slightly because of manufacturing tolerances, or because of wear or damage during use. Also the density may not be perfectly uniform throughout the material. These factors may mean the CG does not coincide with the geometric centre or axis of rotation. vibrate will Shakin w É mywillbe it Figure 13 CG may not coincide with the geometric centre or axis of rotation. The unbalanced condition will cause vibration during rotation. To rectify this problem the CG must be shifted to make it the same point as the centre of rotation. This can be done by adding small masses of material to the light side of the component, or by removing small masses of material from its heavy side until it balances (Fig 14). The propeller’s supporting mandrel or spindle rolls freely on a pair of horizontal knife edges with very little friction. This kind of balancing is also called mass balancing. The heaviest blade moves downward. When perfectly balanced the propeller will remain stationary in any position to which it is turned. Care must be taken that even slight air movements do not cause wrong indication of balance or imbalance. 1 wheel Many other rotating components are balanced during manufacture. Examples include landing-gear 3 2 rotors, compressors, assemblies, helicopter u turbines, s 6 fans, and the rotors in generators, magnetos, and gyroscopes. Some of these may require re-balancing during reconditioning procedures following wear, damage, or replacement of parts. For a component spinning at very high speed even a tiny amount of unbalance may produce excessive vibration. Therotating components are balancedduring manufacture wheel Landing gear helicopterrotors compressor turbines Fans rotors in generator magnetos gyroscope Feb 2022 36  Emirates Engineering Training the extends Figure 14 Propeller in a static balancing rig guys Stress seiistes Stress is the force acting through a section of solid material and defined as force per unit area. not athingis formulaas changeof stress same = WORN becauseof pressure iii stress it f Strain called msn.netii Strain is the deformation of the material as a result of the stress. If the strain is less than the material’s elastic limit, the elasticity of the material will allow it to return to its natural length. Strain below the elastic limit is directly proportional to the applied stress (Hooke’s Law). Doubling stress will double the strain, (below the elastic limit). If the cross sectional area of the bar is 2 sq m, then the stress will be. nisi If it was 0.5 m long and extends by 2 mm, what is the strain? d ÉÉhhhf stress apply andwhen meanswhenyou extend will object it length tothe Feb 2022 37  Emirates Engineering Training increase in height Always extending Tension Example Tension describes forces that tend to pull an object apart (Fig 15). Flexible steel cable used in aircraft control systems is an example of a component designed to withstand tension loads. Figure 15 Tension forces tend to pull an object apart caused by compress Compression squaring riveting always example Compression is the resistance to an external force that tries to push an object together. The weight of an aircraft causes compressive stress to the runway. Aircraft riveting is performed using compressive forces. When compression loads are applied to the rivet head, the rivet shank will expand until it fills the hole and forms a butt to hold the materials together. l Feb 2022 38  thing mechanical bolt Emirates Engineering Training is a nut and Example aircraft Shear Stress ftp.ghh gaerside of metadata g Shear stresses occur when external forces distort a body so that adjacent layers of material tend to slide over one another. Shear stress tries to tear a body apart (Fig 17). Shear stress may also occur in fluids, for example a layer of oil or grease between two sliding metal surfaces. Some molecules of lubricant cling to each sliding surface. The subsequent layers of lubricant tend to slide over each other to reduce friction between the metal surfaces. side 9right ain't side is I Figure 17 Shear stress tries to tear a body apart. An aeroplane wing or a helicopter rotor blade is very similar to a plank or board. Aerodynamic and gravitational forces try to bend the wing or blade upwards and onwards. Consequently, the top and bottom surfaces of the wing are under alternating compression and tensile stresses and must be constructed to withstand the fatigue that could develop from this situation. During operation, moving parts experience a variety of loadings, caused by vibration, changes of load, and temperature changes. Repeated applications of small loads may eventually result in fatigue failure. Fatigue failures are quite common in aircraft and motor cars, and are at least as common as overload failures. Bending Feb 2022 39  Summary 1 stress it is anexternalforceactingonanobjectperunitcrosssectionalarea Stress fA 2 Strain outcomeofthestressanditisnotmandatorytohaveastraineverytimeyouapply stress strain ff e 3 elasticity Types of stress TÉñÉi n it resultsfromtendingtopull an objectapart Flexiblesteelcable Exp Compicision resistancetoexternalforcetopushanobjecttogether Aircraftrivetin Exp Sheffstressoccurs forcedistortabody fff gn whenexternal fffff.eeFno fainagmthtal ftp aataf ytef Torsionalstress Bending 5A In flight influence ofaerodynamicloads Bending upward on topthewing compression belowwing tension 5B on ground influenceof gravity on topwing tension belowwing Bending downward compression  Emirates Engineering Training twisting Torsional Stress Torsion or torque is a form of shear stress. If a twisting force is applied to a rod that is fixed at one end, the twist will try and slide sections of material over each other. The result is that, in the direction of the twist, there is compression stress and in the direction opposite to the twist, tension stress develops. A crack can originate at the point of highest tensile stress in a part. Such a crack can grow progressively and the part’s strength is reduced so much that it suddenly breaks. Residual Stress (“Locked In Stress”). Abrupt or uneven temperature changes tend to cause internal stress. This often occurs when heat-treating metals. This effect often explains why a component fails in service even though its externally applied stress levels are low. Residual Stress can be beneficial. The controlled crazing of some car windscreens in a crash or when hit by a stone, is achieved by building residual stress into the glass when the windscreen is made. Figure 19 Torsional stress Pressure depends on Area Both liquids and gases are fluids, therefore the theory behind buoyancy and pressure in liquids, such as water, and gases, such as air, is similar. (Fig 20). An important difference to remember, though, is that liquids are considered incompressible, that is, have a constant density, while gases are compressible. was p p E P 100NM P 25MAR Figure 20 Pressure between solid surfaces Feb 2022 40  pressure in state of matter Reinsolid depends on Area P A PT so P α incompressible solids are defined pressure are pressure in liquid depends in depth only density night PE Pgh 9.8m1s2 pr.ESfqidfpavity Pressure α depth in Pressure gas p depends on tumpreture  Emirates Engineering Training Pressure is defined as ‘force per unit area’ (Using g = 10 m/s per s) This explains why high heel shoes do more damage to wooden floors, and wide wheels distribute a car’s weight over the tarmac. Pressure in Fluids Pressure is still defined as ‘force per unit area’, but in a fluid it is caused by the continual bombardment of the molecules against the inside of the container. The pressure exerted by a column of liquid is determined by the vertical height of the column, gravity, and the density of the fluid. (Fig 21). Figure 21 The amount of fluid has no effect on pressure at the bottom of the column where p = density kg/m3 m = mass kg devices follows Hydrometer and archimedes principlevalue h = depth m the exact Density and Specific Gravity tod measure 56 5 so Desire of SG 56 8 gravities can be determined. Gasoline has a specific gravity of 0.72, which means its weight is 72% of the same amount of water. water less than one so it willfloaton Feb 2022 41 roae io submerged  Emirates Engineering Training now waiting i her 50 sumberged ans howmuch it will be Gases are compared to air to obtain an SG. 6 if56 0.8 80 answer Note: The term Relative Density is used to compare the density of air at different altitudes to sea level. The SG of aviation fuel varies due to a variety of factors such as: Refining process; Storage facilities; Ambient conditions. 3 The pilot or engineer must check the SG of the fuel supply, to calculate how many litres will provide the weight of fuel requested. Weight of fuel = Volume (litres) x SG volumeof displacewater ofwater volume Buoyancy might Bouynalyforce Archimedes principle states that an item placed in fluid will displace a volume of fluid equal to its own volume. Furthermore, the object submerged in the fluid is supported by a force equal to the weight of the fluid displaced. This is the buoyancy force. Therefore if a body displaces more fluid than its own weight it will float. volume mefthbox ofdisplacedwa rchimede principle 0 displaced ff Figure 22 Buoyancy Weigh upthrustforce Feb 2022 42  Emirates Engineering Training will float SG KSS will sink so Figure 23 Three bodies of the same volume more Three bodies of the same volume but of different SG’s are shown either floating or submerged in water: a Body A with SG of 0.25 – only ¼ submerged Body B with SG of 0.5 – only ½ submerged IIu Body C with SG of 2 – will not float in water – weight is ½’d though If tank were filled with fluid with SG greater than 2 – Body A and B would float higher, and body C would also float – ships float higher in salt water than in fresh water. Lower density materials float on higher density materials. For example: Gasoline or oil will float on water; Water sinks to the bottom of a petrol tank. Ice will float on water; Lead will float on mercury but sink in water. Pressure Pascal’s Principle relatedtoliquids Pascal’s law states, ‘Pressure applied to an enclosed fluid is transmitted undiminished to every part of the fluid, as well as to the walls of the container. (Fig 24). remains same everypoint fhfhatehessw pressure every.gg pre same ii hI B Pn The same volume of fluid is displaced at each end of the system, 1 psi spread over 10 square inches can support 10 lb. so, MA = 10. Feb 2022 43  Emirates Engineering Training P EA proportion pressure is inversly to Arer Note that the large piston will only move up 1/10 of the distance the small piston moves in. If a piston such as the above is used to drive in both directions an interesting situation occurs. The same pressure provides different forces according to direction of travel due to the differing area available. This will also affect the speed at which the operation will occur. th mA L 1 Pressureissame everywhere Figure 25 Mechanical advantage obtained in a hydraulic system. Measurement of Pressure Atmospheric pressure at a location then depends on the weight of the column of air above that location (typically 14.7 psi at sea level up to 4.4.psi at 29,000 ft). Gauge pressure reads pressure above (or below) atmospheric pressure, tyre pressure gauges read Gauge pressure. An absolute pressure gauge reads line pressure plus atmospheric pressure. attitude α sure Resowing Atmospheric pressure altitude pressure atmospheric pressure molecules on head less weightlow less your are high atmospheric pressure you molecules on head moreweight high more your are below you atmosphere atmospheric no gauge pressuret pressure atmosphericpressure absolute pressure Gauge pressure atmosphericpressure differential pressure gauge pressure outsidepressure inside pressure Feb 2022 44  Emirates Engineering Training For passenger comfort, modern aircraft retain a cabin altitude equivalent to 8000’ or 11 psi. Cruising at 29,000 ft, the outside pressure is 4.4 psi. Therefore, the structure of the aircraft is experiencing a differential pressure of: 11 - 4.4 = 6.6 psi This is a significant component of the total stress on the airframe. Properties of Solids, Liquids and Gases Solids have a definite shape and a definite volume which is independent of its container. In a solid the forces (bonds) that keep the atoms or molecules together are strong. Therefore, a solid does not require outside support to maintain its shape. Most metals are solids and as such are usually hard and strong and capable of being shaped mechanically, (malleable and ductile). Both liquids and gases are classified as fluids. At any point on the surface of a submerged object, the force exerted by a fluid is perpendicular to the surface of the object. The force exerted by the fluid on the walls of the container is perpendicular to the walls at all points. Although liquids and gases both share the common characteristics of fluids, they have distinctive qualities of their own. A liquid is regarded as incompressible, (fixed density) whereas a gas is comparatively easy to compress. A change in volume of a gas can easily be achieved by changes of temperature and/or pressure. A given mass of gas has no fixed volume and will expand continuously unless restrained by a containing vessel. Feb 2022 45  Emirates Engineering Training TOPIC 2.2.2 - KINETICS Kinetics is all about states of motion. We will look at how objects can transfer from place to place, and in some cases have a motion whilst not actually getting anywhere! DISPLACEMENT AND DISTANCE Displacement refers to the position of an object relative to its point of origin. This is different to distance which is the total length travelled by an object from its point of origin. Displacement takes direction into consideration, but distance does not care about direction. The aircraft may travel a total distance of 2 km as it veers left and right, but its displacement, measured only as the difference between the start point and finish point, will be less. The displacement of the aircraft in an easterly direction only is less again. agreed long always straightline rector scalar Displacement Figure 1 Displacement and Distance distance is always greater than displacement displacement always shorter Line the starts displacement alway e final fromintialpo.to Feb 2022 46  Emirates Engineering Training rector speed fight velocity planedirectionEffie escolar SPEED AND VELOCITY A similar distinction can be made between speed and velocity. They both refer to the distance travelled per unit of time, for example, miles per hour, metres per second etc. However, velocity is a vector quantity, so direction is important. Speed is a scalar quantity, so direction is irrelevant. Average speed is distance travelled divided by time taken. Figure 2 Speed and Velocity Average velocity is the final displacement divided by the total time. Acceleration Winfree When an object has an initial velocity then, after a period of time, that velocity has changed (increased or decreased), the object is said to have accelerated. Acceleration can be positive or negative. Negative acceleration is called deceleration. Acceleration is the rate of change in velocity. Average acceleration is found by div