Physics him aviation for aviation university basic level

Physics av ppt

1. PHYSICS (GC-2) Ethiopian Aviation Academy Aviation Maintenance Technicians School (AMTS) 1

2. Physics Course Duration - Theory 30 hrs 2

3. Objective Students will get an overview of: Aviation Physics as per the requirement of regulatory bodies The application of the concepts of Physics in the aircraft operation 3

4. Delivery Lecture discussion Class exercise Reading Assignments 4

5. Course contents Matter Statics Kinetics Dynamics Simple Machines Fluid Dynamics Thermodynamics Optics (Light) Wave Motion and Sound 5

6. References:- Aviation Maintenance Technician Handbook General, AC 65-9A Principles of Physics, by F. Bueche 6

7. Introduction The study of physics is important because so much of modern life consists of applying physical principles to our needs. Most machines we use today require a knowledge of physics to understand their operation. 7

8. Besides you will find that the laws , formulae and calculations of physics are important to understand the main principles on which aircrafts are flown and operated.   8

9. Matter and Energy By definition, matter is anything that occupies space and has mass 9

10. Matter is: what all things are made of ; whatever occupies space , and has mass 10

11. Matter cannot be created or destroyed , but it is possible to change its physical state- Law of conservation. 11

12. Chemical Nature of Matter The smallest part of an element that can exist chemically, is the atom 12

13. There are currently 105 known elements or atoms 13

14. Physical Nature of Matter The molecule is the smallest unit of substance that exhibits: the physical and chemical properties of the substance 14

15. All matter exists in one of three physical states: solid, liquid and gas 15

16. Solid A solid has a definite volume and shape , and is independent of its container. Liquid Liquid material conforms to the shape of the container it is held in, an example being a melting ice cube. Gas Gas differs from solids and liquids in the fact that they have neither definite shape nor definite volume 16

17. State Changes ICE WATER STEAM SOLID LIQUID GAS 17

18. Mass and Weight Mass is a measure of the quantity of matter in an object. The mass of an object describes how many molecules or atoms are in the object Regardless of an object’s position, its mass remains constant Mass = Weight ÷ Acceleration due to gravity 18

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20. Weight is a measure of the pull of gravity acting on the mass of an object The more mass an object has, the more it will weigh under the earth’s force of gravity. Because it is not possible for the mass of an object to go away, the only way for an object to be weightless is for gravity to go away . Weight = Mass × Gravity 20

21. Attraction Attraction is the force acting mutually between particles of matter, tending to draw them together. Sir Isaac Newton called this the “Law of Universal Gravitation.” 21

22. Porosity Porosity means having pores or spaces where smaller particles may fit when a mixture takes place. This is sometimes referred to as granular — consisting or appearing to consist of small grains or granules. 22

23. Impenetrability Impenetrability means that no two objects can occupy the same place at the same time . Two portions of matter cannot at the same time occupy the same space. 23

24. Density and Specific Gravity Density The density of a substance is its weight per unit volume . ( weight/density) –expressed in (lb⁄ft 3 ) Or The density of a substance is defined as its mass per unit volume . ( mass /density )-expressed in (g⁄cm 3 ) 24

25. Example A liquid which fills a certain container weighs 1,497.6 lb. The container is 4 ft long, 3 ft wide, and 2 ft deep. Find the density of the liquid. 25

26. Specific Gravity Thus, specific gravity is calculated by comparing the weight of a definite volume of the given substance with the weight of an equal volume of water.. Specific Gravity = Weight of the substance Weight of an equal volume of water Or Specific Gravity = Density of the substance Density of water 26

27. For example If a certain hydraulic fluid has a specific gravity of 0.8, and the density of water is 62.4 lb/ft 3 .Find the weight of 1 ft 3 of the liquid. 27

28. Specific gravity and density are independent of the size of the sample under consideration and depend only upon the substance of which it is made . 28

29. MECHANICS Scalar and Vector Quantities The term scalar means that the quantity possesses magnitude only , Examples: mass, energy, time, temperature, volume, area and length 29

30. Vector quantities possess both magnitude and direction , and if either change the vector quantity changes. Examples of Vector quantities: force, velocity, acceleration, displacement and momentum. 30

31. MECHANICS S calar and Vector Quantities 31

32. Vector diagram 32 Application

33. Moment of a Force The turning effect of a force is called the moment of the force about the axis of rotation 33

34. The moment of a force about a point is dependent on two quantities : the magnitude of the force and the perpendicular distance of the point from the force 34

35. 35 Calculate the moment of the 5N force and 10N force

36. Center of Gravity Center of Gravity (CG) of an object is the point about which its weight is concentrated . 36

37. CG of an aircraft is a point about which the nose heavy and tail heavy moments are exactly equal in magnitude. It is the balance point for the aircraft. 37

38. An aircraft suspended from its CG would have no tendency to rotate in either a nose-up or nose-down attitude 38

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40. Stress Stress is external force exerted per unit area of an object An external force acting on an object causes the stress (  ) to manifest itself in one of five forms, or combination of those five. 40

41. The five forms are:- Tension, Compression, Torsion, Bending, and Shear . 41

42. Tension 42 Tension is a force that tries to pull an object apart .

43. Compression 43 Compression is a force that tries to crush an object.

44. 44 An example of compression is when a sheet metal of an airplane is assembled using the fastener known as a rivet.

45.   Torsion Torsion is the stress applied to a material when it is twisted . Torsion is actually made up of two other stresses: tension and compression . 45

46. Torsion 46

47. Bending Example: An airplane in flight experiences a bending force on the wing as aerodynamic lift tries to raise the wing-This causes the skin on top of the wing to compress and on the bottom to be under tension . Opposite effect appears when the airplane is on ground . 47

48. Shear A shear stress attempts to slice or shear a body apart , like a knife cutting through butter. 48

49. Strain When the material of a body is in a state of stress; deformation takes place and changes the size and shape of the body. 49

50. Strain If the stress acting on an object is great enough, it can cause the object to change its shape or to become distorted. When an object becomes distorted by an applied force, the object is said to be strained. Strain (  ) = elongation = Δ L / L o original length 50

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52. Elasticity Elasticity can be characterised by a linear relationship between stress and strain at small values of strain. When the stress induced into a material is removed, it makes a complete recovery to its original size. 52 E =  / 

53. Modulus Modulus is a measure of the quality of hardness or rigidity of a material Modulus= Stress / Strain 53

54. Pressure in Liquids Pressure (p) is the measurement of a force (F) exerted over a given area (A) P = F/A - The force is measured in pounds and the surface area in square inches , making unit of pressure pounds per square inch or psi, N/m 2 .... 54

55. Standard day atmospheric pressure is equal to: 14.7 psi, 29.92 inches of mercury ("Hg), 760 millimeters of mercury (mm Hg), or 1013.2 millibars. 55

56. Gauge Pressure Gauge pressure ( psi g ) is the pressure read directly from a gauge and represents the pressure in excess of the pressure in the atmosphere. Example : When a gas bottle is opened to the atmosphere and all the gas has escaped, the bottle gauge reads zero although it still contains the atmospheric pressure of 14.7 psi inside. 56

57. Absolute Pressure When pressure is referenced from zero pressure rather than from atmospheric pressure, this is known as absolute pressure ( psi a ) Absolute pressure is equal to gauge pressure plus atmospheric pressure. An absolute gauge will indicate the atmospheric pressure of 14.7 psi when it is technically empty 57

58. Differential Pressure Differential pressure ( psid) is the difference between pressures being read at two different locations within a system. Aircraft use differential pressure gauges as the air speed indicator ( ASI ), which measures the difference between the ram air pressure and the static air pressure 58

59. Buoyancy Archimedes’ Principle states that when an object is submerged in a liquid; The object displaces a volume of liquid equal to its volume and Is supported by a force equal to the weight (W) of the liquid displaced. The force that supports the object is known as the liquid's up-thrust (U). 59

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61. Example: A 10-ft 3 object weighing 700 lb is placed in pure water. Will the object float? If the object sinks, what is its measurable weight in the submerged condition? 61

62. KINETICS The spatial difference between initial position and final position is displacement . 62

63. Uniform Motion Motion may be defined as: A continuing change of: position or place , or The process in which a body undergoes displacement. 63

64. When an object is at different points in space at different times, that object is said to be in motion , If the distance the object moves remains the same for a given period of time, the motion may be described as uniform . 64

65. Speed and Velocity Speed refers to how : fast an object is moving, or far the object will travel in a specific time. 65

66. The speed of an object tells nothing about the direction an object is moving To calculate the speed of an object, the distance it travels is divided by the elapsed time. 66 v  =  s t

67. For example , if the information is supplied that an airplane leaves New York City and travels 8 hours at a speed of 150 mph. This information tells nothing about the direction in which the airplane is moving. At the end of 8 hours, it might be in Kansas City, or if it traveled in a circular route, it could be back in New York City. 67

68. Velocity is the quantity which denotes both the speed of an object and the direction in which the object moves. Velocity can be defined as the rate of motion in a particular direction. Velocity is also described as being a vector quantity. 68

69. displacement (s) Linear velocity (v) = _____________ time taken (t) 69

70. Relative Velocity If an aircraft (A) is flying north at 500 knots then, relative to a second aircraft (B) flying north at 400 knots, the first aircraft is travelling at 500 - 400 = 100 knots 70

71. If the second aircraft B had been flying southward at 400 knots, the first aircraft A would be flying northward relative to B at: 500 - (- 400) = 900 knots 71

72. Acceleration Acceleration is defined as the rate of change of velocity. 72

73. Example: An Air Force F-15 fighter is cruising at 400 mph. The pilot advances the throttles to full after burner and accelerates to 1,200 mph in 20 seconds. What is the average acceleration in mph/s and fps/s? 73

74. Motion Newton’s Law of Motion Newton's first law of motion explains the effect of inertia on a body. Inertia is responsible for the discomfort felt when an airplane is brought to a sudden halt in the parking area and the passengers are thrown forward in their seats. It is a property of matter . 74

75. Newton’s First Law states that: Objects at rest tend to remain at rest and objects in motion tend to remain in motion at the same speed and in the same direction, unless acted on by an external force. 75

76. Newton’s Second Law Newton’s second law states that the acceleration produced in a mass by the addition of a given force is directly proportional to the force, and inversely proportional to the mass F = m a 76

77. Newton’s Third Law Newton’s third law of motion is often called the law of action and reaction. It states that for every action there is an equal and opposite reaction. 77

78. Circular Motion Circular motion is the motion of an object along a path that has a constant radius. When an object moves in a uniformly curved path at uniform rate, its velocity changes because of its constant change in direction For example, if one end of a string is tied to an object and the other end is held in the hand, the object can be swung in a circle. 78

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80. The string exerts a centripetal force on the object, and the object exerts an equal but opposite force on the string, obeying Newton’s third law of motion. The force that is equal to centripetal force, but acting in an opposite direction, is called centrifugal force . Centripetal Force = Mass (Velocity 2 ) = mV 2 Radius r 80

81. Example : What would the centripetal force be if a 10 pound weight was moving in a 3-ft radius circular path at a velocity of 500 fps? 81

82. Periodic Motion The motion/time during which a mass moves away from, and then returns to its original start position is known as periodic motion and the time period respectively. 82

83. Spring If the mass is displaced from its original position and released, the force in the spring will act on the mass so as to return it to that position. It behaves like the pendulum, in that it will continue to move up and down 83

84. The resulting up and down motion can be plotted against time and will result in a typical sinusoidal graph 84

85. Vibration Theory The simple pendulum or spring-mass would according to basic theory, continue to vibrate at constant frequency and amplitude, once the vibration had been started The vibrations die away due to other forces associated with motion, such as friction and air resistance and this is termed Damped Vibration . 85

86. Simple Machines A simple machine is a device that requires only the force of a human to perform work. One of the properties of a simple machine is that it can be used to increase the force that can be applied to a task. 86

87. Simple Machines… There are four types of simple machines: (1) the lever , (2) the inclined plane (the wedge and the screw are special cases of the inclined plane), (3) the pulley , (4) the wheel and axle (including the gear). 87

88. Levers The lever is a simple machine consisting of a rigid bar that is free to pivot on a fulcrum. Depending on the position of the force (F), the load or resistance (R) and the fulcrum, there are three classes of levers: 88

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92. The Pulley Pulleys are simple machines in the form of a wheel mounted on a fixed axis and supported by a frame. Pulleys are used for lifting by attaching one end of the rope to the object, threading the rope through the pulley (or system of pulleys), and pulling on the other end of the rope. The wheel, or disk, is normally grooved to accommodate a rope. 92

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94. Single Fixed Pulley A single fixed pulley is a first class lever with equal arms. When a first class lever has equal arms, the mechanical advantage is 1. The only advantage of a single fixed pulley is to change the direction of the force, or pull on the rope. 94 MApulley = Number of strands holding the resistance

95. Pulley… 95

96. Pulley… Single Movable Pulley A single pulley can be used to magnify the force exerted. acts like a second class lever This type of pulley would have a mechanical advantage of two 96

97. Block and Tackle A block and tackle is made up of multiple pulleys, some of them fixed and some movable. The number of weight supporting ropes determines the mechanical advantage of a block and tackle For the fig. shown, the MA is 4, If the weight was 200 lb, it would require a 50 lb effort to lift it. 97

98. The Gear Two gears with teeth on their outer edges, as shown in the Figure act like a first class lever when one gear drives the other. The effort arm is the diameter of the driven gear, and the resistance arm is the diameter of the drive gear when a large gear drives a small one, the small one turns faster and has less available force. In order to be a force gaining machine, the small gear needs to turn the large one 98

99. Inclined Plane The inclined plane is a simple machine that facilitates the raising or lowering of heavy objects by application of a small force over a relatively long distance. When weighing a small airplane, like a Cessna 172, an inclined plane (ramp) can be used to get the airplane on the scales by pushing it, rather than jacking it. 99

100. Inclined plane… With an inclined plane, the length of the incline is the effort arm and the vertical height of the incline is the resistance arm. 100

101. Inclined plane… Example : The Cessna 172 in Fig. above weighed 1,600 lb on the day of the weighing. The ramp it is sitting on is 6 in tall (arm) and the length of the ramp is 24 inches (effort arm). calculate the force needed to push the airplane up the ramps 101 Effort (E) × Effort Arm (L) = Resistance (R) × Resistance Arm (l) E × 24 in = 1,600 lb × 6 in E = 1,600 lb × 6 in ÷ 24 in = 400 lb

102. 102 Efficiency = Work output x 100% Work Input

103. Dynamics 103

104. Force Force is the intensity of an input. For example, if we apply a force to an object, the tendency will be for the object to move. Another way to look at it is that for work, power, or torque to exist, there has to be a force that initiates the process. F= m x a The unit for force:- Pound, Newton 1pound=4.448 Newton's Inertia Inertia is the resistance of a body to movement.   104

105. Work Work is done when a resistance is overcome by a force acting through a measurable distance . If a force is applied to an object and the object moves, work is done To calculate work, the following formula is used: Work = Force (F) × distance (d) The unit of work:- foot-pound or inch-pound (in the English system) or N-m (in metric sys.) 1m=3.32feet, 1pound=4.448N 105

106. Example: How much work is accomplished by jacking a 150,000-lb Airbus A-320 airplane a vertical height of 3 ft? 106

107. Example: How much work is accomplished when a tow tractor is hooked up to a tow bar and a Boeing 737-800 airplane weighing 130,000 lb is pushed 80 ft into the hangar? The force on the tow bar is 5,000 lb. 107

108. Power Power is defined as the rate of doing work . That is, how long does it take to accomplish the work. Power can be calculated by: Power = (Force x Distance)/time The unit of power is ft-lb/s or N-m/s 1 hp = 550 ft-lb/s 1 hp = 746 watts (electricity conversion ) 108

109. Example : What power would be needed, and also horsepower, to raise the GE-90 turbofan engine into position to install it on a Boeing 777-300 airplane? The engine weighs 19,000 lb, and it must be lifted 4 ft in 2 minutes. 109

110. Example: How much power is required to raise an aircraft weighing 25 000 kg, 2 metres in 30 seconds? 110

111. Torque Torque is described as a force acting along a distance , where as work is described as a force acting from first to last a distance. Torque is something that creates twisting and tries to make something rotate . The formula for torque is: Torque = Force × distance - the distance value in this formula is not the linear distance an object moves, but rather the distance along which the force is applied.. 111

112. For the cylinder in Fig. below, there is a force of 500 lb pushing down on the top of the piston. The connecting rod attaches to the crankshaft at an offset distance of 4 in. The product of the force and the offset distance is the torque, in this case 2,000 lb-in. 112

113. Energy Energy is typically defined as something that gives us the capacity to perform work . Energy can be classified as one of two types: either potential or kinetic. 113

114. Potential Energy Potential energy is defined as being energy at rest, or energy that is stored . Potential energy may be classified into three groups: that due to position, that due to distortion of an elastic body, that which produces work through chemical action . 114

115. To calculate the potential energy of an object due to its position, as in height, the following formula is used: Potential Energy = Weight × Height PE = m g h - units of PE :( ft-lb ) or inch-pounds ( in-lb ), which are the same units that apply to work. 115

116. Example: A Boeing 747 weighing 450,000 pounds needs to be raised 4 feet in the air so maintenance can be done on the landing gear. How much potential energy does the airplane possess because of this raised position? 116

117. Kinetic Energy Kinetic energy is defined as being energy in motion. To calculate the kinetic energy for something in motion, the following formula is used: Kinetic Energy = 1⁄2 Mass × Velocity 2 Kinetic energy has the same units as potential energy, namely foot-pounds or inch-pounds. 117

118. Example : A Boeing 777 weighing 600,000 lb is moving down the runway on its takeoff roll with a velocity of 200 fps. How many foot-pounds of kinetic energy does the airplane possess? 118

119. Heat Energy Heat energy is defined as ‘the energy in transit between two bodies due to a difference in temperature’ 119

120. Energy 120

121. Conservation of Energy Energy cannot be created or destroyed, but it can only be transformed from one state to another  The Law of Conservation of Energy states that: ‘During transformation of energy from one form to another, the total amount of energy is unchanged .’ 121

122. Momentum Momentum or total ‘quantity of motion’ of a body is the product of its mass and velocity. Momentum of a body = m v 122

123. Conservation of Momentum 123

124. In accordance with Newton’s Third Law, the impulse forces will be equal and opposite. After the impact, A and B will have new velocities. By calculation, it can be proven that the momentum before the impact equals the momentum after the impact 124

125. Friction There are three kinds of friction: (1) starting (static) friction, (2) sliding friction, and (3) rolling friction. f = μ N Where: f=friction μ =coefficient of friction N=Normal force 125

126. For example, if the coefficient of sliding friction of a smooth iron block on a smooth, horizontal surface is 0.3, the force required to start a 10 lb block would be: 126

127. Example: An aircraft with a gross weight of 79,600 lb is towed over a concrete ramp. What force must be exerted by the towing vehicle to keep the airplane rolling after once set in motion? (The value of “ μ ” for rubber tires on concrete is about 0.02.) 127

128. Rotating Masses A rotating mass can be an aircraft wheel, engine flywheel or a gyroscope and used on a number of places on aircraft. Gyroscopes are used in several of an aircraft’s instruments, which are vital to the safe operation of the aircraft. All rotating mass components operate correctly if they are perfectly balanced. 128

129. Gyroscope The gyro consists of a rotor, which spins on an axis that is connected to an inner ring, and this in turn is connected to an outer ring The outer ring is attached to the gyro frame and all the attaching points are at 90  to the previous one. The gyro frame can be attached to a simple support plate or the structure of an aircraft. 129

130. Gyroscope 130

131. Rigidity and Precession A rotor rotating or spinning, its mass gains angular momentum it exhibits resistance to any change of axis of rotation for any external force. This resistance is termed Rigidity . 131

132. Precession If sufficient force or torque is applied to tilt the rotor, the movement of the gyroscope is known as Precession. A rotor precesses or moves 90 degree away from the point of application of the force. 132

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134. Fluid Dynamics Density : The density of a substance is its mass per unit volume and it uses the Greek symbol Rho (  ). The density of solids and liquids vary with temperature, and the density of a gas varies with both temperature and pressure. Density (  ) = Mass / Volume 134

135. Density of materials 135

136. Relative Density Relative Density (formerly known as Specific Gravity) is calculated by comparing the weight of a definite volume of substance with an equal volume of water. Relative Density = Mass of any volume of a substance Mass of equal volume of water 136

137. Example : liquid in a container has a mass of 756 kilograms, and its dimensions are 1.6 m long, 1.0 m wide and 0.75 m deep. Find the density of the liquid? 137

138. Hydrometer A device called a hydrometer is used to measure the relative density of liquids. This device has a glass float contained within a cylindrical glass body. The float has a weight in the bottom and a graduated scale at the top. When liquid is drawn into the body, the float displays the relative density on the graduated scale 138

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140. Viscosity Viscosity is a measure of the resistance to flow Liquids such as water flow very easily whilst others, such as treacle, flow much slower under the same conditions. Liquids of the type that flow readily are said to be mobile and those of the treacle type are called viscous , and is due to liquids interior friction. 140

141. Streamline Flow When a fluid, liquid or gas is flowing steadily over a smooth surface, its narrow layers follow a smooth path, known as streamlines or laminar flow. If this flow meets large irregularities the streamlines are broken up and the flow becomes turbulent It can be found by experiment, that as the fluid speed increases to pass the narrowest part of the tube, the dynamic pressure falls 141

142. 142 - A tube which tapers smoothly to a narrow constriction, and then widens out again is known as a Venturi tube . - When a steady stream of liquid passes through such a tube, the streamlines crowd together and speed up as the restriction narrows

143. Turbulence and Skin Friction The resistance to fluid flow can be divided into two general groups: skin friction and turbulence 143

144. Skin Friction 144 Skin friction is the resistance present on the surface of flat plate , which has a flow over it. The fluid is slowed up near the surface owing to the roughness of the surface

145. Turbulence The second form of resistance is known as eddies or turbulent airflow, which can be demonstrated by placing the flat plate at right angles to the flow 145

146. Buoyancy A solid body submerged in a liquid or a gas weighs less than when weighed in free space. This is because of the upward force, called buoyant force , which any fluid exerts on a body submerged in it. An object will float if this upward force of the fluid is greater than the weight of the object. 146

147. Objects denser than the fluid, appear to lose a part of their weight when submerged. The buoyant force which a fluid exerts upon a submerged body is equal to the weight of the fluid the body displaces - Archimede’s principle Buoyant Force = Volume of Object × Density of Fluid Displaced The volume of irregular shaped objects can be measured by this method 147

148. Example: A 10-ft 3 object weighing 700 lb is placed in pure water. Will the object float? If the object sinks, what is its measurable weight in the submerged condition? If the object floats, how many cubic feet of its volume is below the water line? Buoyant Force = Volume of Object × Density of Fluid Displaced = 10 (62 = 624 lb Because the buoyant force is less than the object weighs, the object will sink. The difference between the buoyant force and the object’s weight will be its measurable weight, or 76 lb. 148

149. The Gas Laws Boyle’s Law : Boyle’s law is normally stated as: “The volume of an enclosed dry gas varies inversely with its absolute pressure, provided the temperature remains constant.” P 1 V 1 = P 2 V 2 149

150. Example : 10 ft 3 of nitrogen is under a pressure of 500 psia . If the volume is reduced to 7 ft 3 , what will the new pressure be? 150

151. Charles’ Law The French scientist, Jacques Charles found that: all gases expand and contract in direct proportion to the change in the absolute temperature, provided the pressure is held constant V1T2 = V2T1 or V1/T1 = V2 /T2 Charles’ law also works if the volume is held constant, and pressure and temperature are the variables. In this case, the formula would be as follows: P1T2 = P2T1 151

152. Example : A 15-ft 3 cylinder of oxygen is at a temperature of 70°F and a pressure of 750 psig. The cylinder is placed in the sun and the temperature of the oxygen increases to 140°F. What would be the new pressure in psig? 70 degrees Fahrenheit = 530 degrees Rankine 140 degrees Fahrenheit = 600 degrees Rankine 750 psig + 14.7 = 764.7 psia P1T2 = P2T1 764.7 (600) = P2 (530) P2 = 764.7 (600) ÷ 530 P2 = 865.7 psia = 851 psig 152

153. General Gas Law By combining Boyle’s and Charles’ laws, a single expression can be derived which states all the information contained in both. This allows calculation of pressure, volume or temperature when one, or more of the variable changes The formula which is used to express the general gas law is as follows: . P1 V1/T1 = P2 V2/T2 or P1V1T2 = P2V2T1 153

154. 1 Example : 20 ft 3 of the gas argon is compressed to 15 ft 3 . The gas starts out at a temperature of 60°F and a pressure of 1,000 psig. After being compressed, its temperature is 90°F. What would its new pressure be in psig? 60 degrees Fahrenheit = 520 degrees Rankine 90 degrees Fahrenheit = 550 degrees Rankine 1,000 psig + 14.7 = 1,014.7 psia P1 (V1) (T2) = P2 (V2) (T1) 1,014.7 (20) (550) = P2 (15) (520) P2 = 1,431 psia P2 = 1,416.3 psig 154

155. Fluid Pressure A fluid (liquid, vapour or gas) in a container exerts a pressure on the walls of that container, at right angles to the surface P=F/A or Force = Pressure × Area The basic unit of pressure is derived from a force divided by an area. In the SI system----(N/m 2 ), Pascal (Pa), Bar In the British system-----psi, in Hg 155

156. Static Pressures Static pressure usually refers to the pressure measurement taken at a given point with no relative motion between either the point of measurement and the fluid flow Static Pressure =  g h 156

157. Dynamic pressure Dynamic pressure is the measurement of fluid flow when there is a relative motion between the point of measurement and the fluid. Dynamic Pressure = ½  v 2 157

158. Total pressure Total pressure is simply the addition of static and dynamic pressure, to give a total figure, and this represents the pressure that is measured by the pitot tube. Total Pressure = Static Pressure + Dynamic Pressure P total =  g h + ½  v 2   158

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160. Bernoulli’s Principle Bernoulli’s principle was originally stated to explain the action of a liquid flowing through the varying cross-sectional areas of tubes. A tube constructed in the manner shown in the fig is called a “venturi,” or “venturi tube.” 160

161. Bernoulli’s principle is extremely important in understanding how some of the systems used in aviation work, including how the wing of an airplane generates lift The wing on a slow moving airplane has a curved top surface and a relatively flat bottom surface. The curved top surface acts like half of the converging shaped middle of a venturi. 161

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163. As the air flows over the top of the wing, the air speeds up, and its static pressure decreases. The static pressure on the bottom of the wing is now greater than the pressure on the top, and this pressure difference creates the lift on the wing. 163

164. Thermodynamics Heat is a form of energy that causes molecular agitation within a material. The amount of agitation is measured in terms of temperature, which is a measure of the kinetic energy of molecules Heat may also be defined as the total kinetic energy of the molecules of any substance. 164

165. Heat is a form of energy. It is produced only by the conversion of one of the other forms of energy Heat may also be defined as the total kinetic energy of the molecules of any substance. the energy associated with kinetic energy of the molecule is called thermal energy thermal energy transferred from high temperature object to lower temperature object because of the temperature difference is called heat energy 165

166. Heat conversion 166

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168. Heat can be converted to and extracted from other forms of energy like: mechanical energy, electrical energy, chemical energy, nuclear energy. Ex. Compression and expansion of gases ME HEAT 168

169. Absolute Zero Absolute Zero is the point at which all molecular movement will cease and it happens at - 273.15  C or Zero Kelvin. 169

170. Temperature Conversion  C = 5 / 9 (  F - 32)  F = (  C x 9 / 5 ) + 32 Degrees Kelvin =  C + 273 Degrees Rankine =  F + 460 170

171. 171 HEAT the energy associated with kinetic energy of the molecule is called thermal energy thermal energy transferred from high temperature object to lower temperature object because of the temperature difference is called heat energy

172. 172 UNITS CALORIE (cal) BRITISH THERMAL UNIT (Btu) JOULES (J) 1cal = 4.184J 1Btu = 1054J 1Btu = 252cal

173. 173 HEAT TRANSFER Heat energy flows from hot body to cold body but not vice versa. Method of heat transfer Conduction Convection Radiation

174. 174 Conduction Increase in molecular energy is passed along by actual contact Factors Heat conductivity (material property) Cross sectional area (contact area) Thickness

175. 175 Convection Heat transfer by actual movement of heated fluids Factors Surface area (fins, grid) Fluid speed (pump, fan )

176. 176 Convection Heat transfer by actual movement of heated fluids Factors Surface area (fins, grid) Fluid speed (pump, fan )

177. 177 Radiation It is the continuous emission of energy in the form of electromagnetic waves from the surface of all bodies. Factors Material Temperature Color Surface finish

178. 178 HEAT CAPACITY Quantity of heat required to rise the temperature of the body by 1 o c. Factors Mass (weight) Material (specific heat capacit y)

179. 179 SPECIFIC HEAT CAPACITY (C) The quantity of heat which must flow into or out of a unit mass of a substance to change its temperature by one degree is called specific heat capacity C = Q/m T Q = cm T

180. 180 THERMAL EXPANSIAON An overall change in dimension (volume) which is observed in solids, liquids and gases as a result of temperature increase. T   expansion, water to vapor T   contraction, water to ice

181. 181 EXPANSION Factors Material (coefficient of expansion) Magnitude of temperature change L = k  t

182. 182 SOUND

183. 183 WAVE Some kind of propagating disturbance Sound wave  propagation of pressure fluctuation Electromagnetic wave  rapidly oscillating electric and magnetic field Water wave change in position of water surface

184. 184 MECHANICAL WAVE It involves oscillation of medium particles but particles don’t progress with wave. Types of mechanical waves Transverse wave Longitudinal wave

185. 185 TRANSVERSE WAVE Particles move up and down while wave moves at right angle to these up and down motion; Ex. Water wave

186. 186 WAVE MOTION Wave motion involves Wave motion at constant speed (v) Particle vibrate harmonically vibration frequency = f These two motions are related by V = f

187. 187 LONGITUDINAL WAVE Particles of the wave vibrate back and forth longitudinally in the direction of propagation. Eg . Sound wave

188. 188 WAVE LENGTH The distance from one crest to next crest It is the distance a wave moves while a particle complete one full cycle.  CREST TROUGH

189. 189 SOUND It is the propagation of pressure disturbance COMPRESSION RAREFACTION

190. 190 TYPES OF SOUND WAVE Depending on the sensitivity of human ear to sound wave frequency, we have three types of sound wave. Audible wave  20-20,000hz Infrasonic wave  < 20hz Ultrasonic wave  > 20,000hz

191. 191 SOUND TRANSMISSION Three elements are necessary for transmission Source Medium Detector The source will vibrate and cause pressure fluctuation in the medium. The pressure fluctuation in the medium in turn vibrates elements of detector.

192. 192 REFLECTION OF SOUND WAVE When advancing wave encounter a medium of different character some of its energy is reflected back and some is transmitted to the second medium. Eg . Echoes i r

193. 193 PROPERTIES OF SOUND Speed of sound Different in different medium V solid > v liquid > v gas Factors * Material (density, elasticity) * Temperature (gases)

194. 194 SOUND FREQUENCY Different frequency waves have different tones It greatly affect sound energy Sound frequency depends on: Frequency of source Relative motion between source and detector. (Doppler effect)

195. 195 SOUND INTENSITY It is the sound energy per unit area . Intensity is proportional to Square of frequency Square of amplitude Density of the medium Velocity of propagation * Intensity is inversely proportional to the square of the distance from the source.

196. 196 LOUDNESS It is the judgment made by the human ear to determine the sound level . Loudness is proportional to logarithm of intensity. Sound level in db = 10 log ( i /i ) I = 1pw/m 2 = 10 -12 W/m 2 THE LOWER LIMIT OF THE SOUND INTENSITY JUST AUDIBLE TO THE AVERAGE EAR

197. 197 LIGHT

198. 198 NATURE OF LIGHT Light is neither a pure wave phenomena nor a pure particle phenomenon, but electromagnetic radiation with both wave and particle properties Light is elctromagnetic wave which can be perceived by our eye.

199. 199 PROPERTIES OF LIGHT Speed of light (C) = 3 x 10 8 m/s (electromagnetic wave propagation speed) Light moves in straight line within single medium. Different frequency of light appear with different color. Range of wavelength for light 380 nm – 780 nm

200. 200 LAW OF REFLECTION Angle of incident is equal to angle of reflection The incident ray, the reflected ray and the normal to the surface lie in the same plane

201. 201 REFRACTION When light pass obliquely from one medium to another medium, there is a change in direction of propagation. This phenomenon is called refraction of light light medium denser medium

202. 202 LAW OF REFRACTION 1. The ratio of the sine of angle of incidence to sine of angle of refraction is constant independent of the angle of incidence sin  1 / sin 2 = constant 2. The incident ray, the refracted ray and the normal to the surface lie in the same plane

203. 203 INDEX OF REFRACTION

204. 204 The End