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DHL Physics > Definitions > Flashcards

Definitions Flashcards

1
Q

Element

A

-One type of atom
-Cannot be broken down to simpler form by physical or chemical means
-Exists as single atoms or molecules of one atom (Nitrogen)

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2
Q

Valence orbit/electrons

A

-Outermost shell/electrons in outermost shell

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3
Q

Isotope

A

-Variation of an atom that has a different number of neutrons
-Has same number of protons as original
-Has different atomic mass but same atomic number as original
-eg Carbon-12 And Carbon-14 are carbon isotopes

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4
Q

Atomic Number

A

-Number of Protons in an atom

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5
Q

Atomic mass

A

-combined number of protons and neutrons in an atom

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6
Q

Covalent Bond

A

-2 non-metals bonded by sharing electrons
-eg water molecules

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7
Q

Ionic Bond

A

-Bond formed when an atom transfers one or more electrons to another atom
-Atom that loses electrons becomes a POSITIVE ION
-Atom that gains electrons becomes a NEGATIVE ION
-eg Salt (NaCl)

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8
Q

Chemical Compound

A

-pure substance of 2 or more different elements joined via CHEMICAL REACTION
-can only be separated by CHEMICAL MEANS
-has DIFFERENT PROPERTIES to its component elements

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9
Q

Mixture

A

-combination of at least 2 different substances
-NOT chemically bonded
-can be separated by PHYSICAL means
-Each component substance MAINTAINS its original properties

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10
Q

3 categories of Mixture

A
  1. Solutions (sea water)
  2. Suspensions (sand in water)
  3. Colloids (Clouds, milk etc.)
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11
Q

Density

A

-Measurement of mass per unit volume (kg/m^3)
-effects how ‘light’ or ‘heavy’ a material is

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12
Q

Properties of solids

A

-Greatest Force of particle attraction
-particles vibrate about fixed positions
-definite shape and volume
-fixed surface
-high density
-difficult to compress
-expands a little when heated

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13
Q

Properties of liquids

A

-weak force of particle attraction
-random particle arrangement
-particles move freely but remain close
-takes shape of container
-has definite volume
-has a surface
-high density
-cannot be easily compressed
-expands on Heating (more than solid)

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14
Q

Properties of Gas

A

-weak particle attraction
-random particle arrangement
-free and far particle movement
-no definite shape or volume
-no surface
-very low density
-easily compressed
-expands greatly on heating

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15
Q

Endothermic

A

-Reaction that takes in energy from surrounding environment

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16
Q

Exothermic

A

-Reaction that releases heat into surrounding environment

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17
Q

Sublimation

A

-Solid to gas change of state
-skips melting
-doesn’t occur at atmospheric pressure for MOST substances

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18
Q

Deposition

A

-Gas to Solid change of state
-Skips condensation

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19
Q

Newton’s First Law

A

A body will remain at rest or continue to move with a uniform Velocity unless acted on by a FORCE

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20
Q

Vector Quantity

A

-Quantity that has both MAGNITUDE and DIRECTION
-eg Force

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21
Q

Moment (Nm)

A

-Static application of Force
-eg bending a beam

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22
Q

Torque(Nm)

A

-Dynamic application of Force
-eg rotating a shaft

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23
Q

Fulcrum

A

-Centre point about which a force acts
-point from which PERPENDICULAR DISTANCE is measured to calculate moments or torque

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24
Q

Principle of Moments

A

-Two opposing moments must have EQUAL MAGNITUDE in order to balance
-eg balancing a see-saw

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25
Q

Couples

A

-Pair of Forces of EQUAL MAGNITUDE and OPPOSITE DIRECTION

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26
Q

Resultant

A

-Effect of 2 or more VECTORS of the same quantity type (eg two Forces)
-Each vector is a COMPONENT of the resultant
-Resultant = Net result of Components added together/difference between them

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27
Q

Pythagoras to calculate resultant

A

-Resultant = Hypotenuse
-Other 2 sides = Components (Vector quantities)

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28
Q

Scalar Quantity

A

-Quantity with MAGNITUDE but no direction
-Can always be expressed NUMERICALLY

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29
Q

Centre of Gravity

A

-Imaginary point through which weight of object is said to act
-Average location of total weight of aircraft (BALANCE POINT)
-Aircraft CoG given as DISTANCE FROM DATUM

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30
Q

Stress

A

-Describes MAGNITUDE of Force causing DEFORMATION (STRAIN)

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31
Q

5 Basic structural stresses on aircraft

A

1.Tension
2.Compression
3.Shear
4.Bending
5.Torsion

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32
Q

Strain

A

-DEFORMATION of material caused by STRESS
-Presented as RATIO

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33
Q

Tension

A

-Stress that increases Length of material
-As TENSION increases, DEFORMATION increases

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34
Q

Hooke’s law

A

-Extension of an elastic object is DIRECTLY PROPORTIONAL to the FORCE applied to it
-Applies until ELASTIC LIMIT is exceeded

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35
Q

Elastic Limit

A

-Point at which PERMANENT DEFORMATION (Strain) occurs and the ELASTIC REGION ends

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36
Q

Plastic Region

A

-Force and deformation are NO LONGER PROPORTIONAL
-Small force increase = Large amount of deformation
-Material DIAMETER decreases until it fails and BREAKS

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37
Q

Young’s Modulus

A

-Method of measuring ELASTICITY of SOLIDS
-In the ELASTIC REGION the ratio of STRESS and STRAIN is constant
-This constant = Young’s Modulus

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38
Q

Compression

A

-Stress that SHORTENS or SQUEEZES material
-Compressive strength measured in N/m^2

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39
Q

Shear

A

-Stress that SLIDES one layer over another
-Tries to SLICE material

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40
Q

Clevis Bolts

A

-Designed to withstand SHEAR loads

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41
Q

Bending

A

-Stress caused by opposing COMPRESSION and TENSION stresses attempting to BEND a material
-eg Force of LIFT, compressing upper wing and tensioning lower wing causing wing to BEND UPWARDS

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42
Q

Torsion

A

-Stress that TWISTS material
-combination of COMPRESSION and TENSION acting DIAGONALLY at RIGHT ANGLES to each other.

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43
Q

Primary Stress on Propeller shafts

A

-TORSION caused by engine turning opposed by propeller resistance attempting to TWIST the Prop shaft.

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44
Q

Hardness in Solids

A

-Resistance to INDENTATION, PENETRATION and WEAR
-eg Diamonds, Cast Iron

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45
Q

Strength in Solids

A

-Tendency to withstand LOAD without FAILURE or PLASTIC DEFORMATION
-eg Steel, Titanium, Aluminium

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46
Q

Toughness in Solids

A

-Resistance to BREAKAGE when deforming or under IMPACT FORCE
-Do not have to be HARD. SOFT materials can be TOUGH
-eg Hammer head

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47
Q

Brittleness in Solids

A

-Tendancy to BREAK without changing shape
-Weak to SUDDEN or IMPACT Force
-Most materials become BRITTLE when COOLED
-TREATMENT can reduce brittleness and MAINTAIN DESIRABLE QUALITIES
-eg Concrete, Cast Iron and Room temp glass

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48
Q

Elasticity in Solids

A

-Tendency to RETURN TO ORIGINAL SHAPE when distorting Forces are removed
-OPPOSITE of Plasticity
-Each Solids has UNIQUE ELASTIC LIMIT
-eg Hard Steel, Mild + Medium carbon steel and Rubber

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49
Q

Plasticity in Solids

A

-Tendency to STAY IN NEW SHAPE when distorting Forces are removed
-VERY PLASTIC substances will change shape under LIGHT FORCE
-VERY HARD plastic materials require STRONG FORCE to change shape
-eg Lead, gold, aluminium, putty, plasticine and Wet Clay

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50
Q

Malleability in Solids

A

-Tendency to be UNDAMAGED by COMPRESSIVE STRESS
-Malleable materials can be BEATEN, ROLLED or PRESSED into a shape without FRACTURE/BREAKING
-eg Red hot steel, aluminium

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51
Q

Ductility in Solids

A

-Tendency to undergo TENSILE STRESS without damage
-WIRES require DUCTILE MATERIAL (Metal rods are drawn through steel dies during manufacturing)
-eg Copper, Gold, Silver and Steel

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52
Q

Fluid

A

Liquid, Gas or Vapour

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53
Q

Vapour

A

-Gas that can LIQUIFY with a PRESSURE INCREASE without a TEMPERATURE INCREASE
-Also name for Gas below its BOILING POINT
-eg Steam and Sodium Vapour

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54
Q

Volatile Liquid

A

-readily EVAPORATES at room temperature
-quickly occupies space above it with its VAPOUR
-will continue until completely evaporated in an OPEN CONTAINER
-eg Petrol, methylated spirits and Ethanol

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55
Q

Flammable/Inflammable

A

-CATCH FIRE readily
-often a property of VOLATILE LIQUID VAPOURS
-eg Fuels, Cleaning Fluids, some paints and dopes

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56
Q

Flash Point

A

-TEMPERATURE at which COMBUSTABLE liquid will catch fire when exposed to NAKED FLAME
-Lower Flashpoint = Easier to Ignite

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57
Q

Flash Point of Aviation fuel

A

38 degrees Celsius

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58
Q

Flashpoint of Petrol

A

-23 degrees Celsius

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59
Q

Toxicity

A

-How POISONOUS a substance is
-High Toxicity = Poison upon ingestion, inhalation or skin contact
-Usually identified with WARNING SIGNS on containers
-eg Mercury, Chlorine Gas, Arsenic or Biocides

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60
Q

Indications of contact with Toxins

A

-Skin Irritation
-Sore Eyes
-Feeling sick
-Difficulty Breathing

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61
Q

Inert

A

-will not CHEMICALLY COMBINE with another substance
-All Inert substances are GASES
-eg Helium, Neon and Argon

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62
Q

Atmospheric Pressure

A

-FORCE exerted by the WEIGHT of the ATMOSPHERE
-Can vary

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63
Q

Average Atmospheric pressure at sea level

A

-14.7 Psi
-also shown as 1 atmosphere (atm) on Barometers

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64
Q

Mercury Barometer

A

-Most common type
-Vertical glass tube closed at top sitting in open, Mercury filled basin at bottom

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65
Q

Gauge Pressure

A

-Amount of Pressure that measured fluid pressure exceeds ATMOSPHERIC PRESSURE by
-eg tire pressure gauge reading

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66
Q

Ambient Pressure

A

-Pressure in area immediately surrounding an object
-eg Static probe pressure

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67
Q

Absolute Vacuum

A

-Volume that doesn’t contain ANY particles

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68
Q

Absolute Pressure

A

-GAUGE PRESSURE + ATMOSPHERIC PRESSURE
-Uses ABSOLUTE ZERO as a reference point
-eg Barometric Pressure

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69
Q

Archimedes Principle

A

-A body in FLUID is subject to an UPWARD FORCE equal to the WEIGHT of the Fluid it DISPLACES
-Upward Force is known as BUOYANT FORCE

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70
Q

Buoyant Force

A

-Upward Force in ARCHIMEDES PRINCIPLE
-Equal to WEIGHT of the DISPLACED FLUID
-Measured in Newton’s or Pounds (N or Lb)

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71
Q

Example of Buoyancy in gases

A

-Hot Air balloon rising
-Heated Air is LESS DENSE than the cool air it DISPLACES

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72
Q

Floatation

A

-Height of float (positive, negative or neutrally buoyant) expresses as a RATIO
-Flotation ratio shows how much of object is BELOW the waterline

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73
Q

Uniform Motion

A

-Moving by the same distance over a given period of time
-This motion is at a CONSTANT SPEED

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74
Q

Constant Velocity

A

-Moving STRAIGHT at a CONSTANT SPEED (Not ACCELERATING)
-Velocity = change in DISPLACEMENT over TIME

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75
Q

Acceleration

A

-Object moving with a CHANGING VELOCITY (Not Constant)
-Occurs I’d object changes SPEED or DIRECTION
-In LINEAR MOTION, acceleration can only occur with a change in DIRECTION

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76
Q

Speed

A

-SCALAR Quantity (Not directional)
-Objects Moving In opposite direction can have SAME SPEED but DIFFERENT VELOCITIES

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77
Q

Centripetal Force

A

-Keeps objects moving in a CURVED PATH
-Directed towards CENTRE OF ROTATION

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78
Q

Centripetal Acceleration

A

-Result of CONSTANT DIRECTION CHANGE from centripetal Force
-direction change = ACCELERATION

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79
Q

Centrifugal Force

A

-opposite of CENTRIPETAL FORCE
-Acts from CENTRE OF ROTATION OUTWARDS
-Calculated same way as CENTRIPETAL FORCE

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80
Q

Pendulum

A

-Weight suspended in EARTH’S GRAVITY
-Free to PIVOT at its TOP END
-Swings when moved due to GRAVITATIONAL ACCELERATION

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81
Q

Pendulum Damping

A

-Resistive Forces (Friction and Air Resistance) that reduce the AMPLITUDE of the swing.
-Eventually STOPS the pendulum
-Used In aircraft to prevent DAMAGING VIBRATIONS

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82
Q

Vibrations

A

-Mechanical oscillations about an EQUILIBRIUM POINT
-Can be PERIODIC or RANDOM
-Sound and Vibrations linked via ACOUSTICS

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83
Q

Free Vibration

A

-Mechanical system set off with starting input and allowed to VIBRATE FREELY
-System will vibrate at NATURAL FREQUENCY and DAMP down to ZERO
-eg Swingset, tuning fork

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84
Q

Forced Vibration

A

-CONTINUOUS MOTION applied to system
-Vibrates at same frequency as APPLIED FORCE
-AMPLITUDE is dependant on the MAKEUP OF THE SYSTEM

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85
Q

Harmonics

A

-PERIODIC - repeats at STANDARD INTERVALS in a SPECIFIC MANNER
-Are SINUSOIDAL with CONSTANT AMPLITUDE
-Are represented as a SINE WAVE

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86
Q

Isothermal Expansion/Compression

A

-Temperature remains CONSTANT
-As volume INCREASES, Pressure DECREASES and vice versa
-Pressure x Volume is constant

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87
Q

Adiabatic process

A

-No heat transferred to or from system
-Process that occurs within insulative container
-A Fast process with no time for heat transfer is also Adiabatic

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88
Q

Adiabatic Expansion/Compression

A

-As Volume increases, Temperature decreases and vice versa

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89
Q

True Adiabatic

A

-Cannot exist
-Some heat is always lost to the environment

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90
Q

4 types of Thermodynamic Process

A

1.Isothermal - Constant Temperature
2.Isochoric - Constant Volume
3.Isobaric - Constant Pressure
4.Adiabatic - No heat transfer to or from the System

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91
Q

Engine Cycle

A

-Series of THERMODYNAMIC PROCESSES forming a CYCLE that converts HEAT into WORK

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92
Q

Reversible Thermodynamic Process

A

-Can be restored to INITIAL STATE without CHANGING SURROUNDINGS
-Must be in THERMODYNAMIC EQUILIBRIUM with surroundings

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93
Q

True Reversible Process

A

-Impossible
-Some heat always transferred with surroundings
-Is a HYPOTHETICAL PROCESS

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94
Q

Irreversible Thermodynamic Process

A

-CANNOT revert back to INITIAL STATE without CHANGING SURROUNDINGS
-Aka NATURAL PROCESS
-All naturally occurring processes are IRREVERSIBLE

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95
Q

Reciprocating Piston engine cycle

A

-NON FLOW processes convert HEAT into MECHANICAL ENERGY
-CONSTANT VOLUME, INCREASED PRESSURE

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96
Q

Gas Turbine engine Cycle

A

-FLOW processes that convert HEAT into MECHANICAL ENERGY
-CONSTANT PRESSURE, INCREASED VOLUME

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97
Q

4 phases of engine cycles

A

1.Induction
2.Compression
3.Combustion
4.Exhaust

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98
Q

4 processes of Otto Cycle (Piston Engine)

A
  1. Adiabatic Compression (1 to 2): Piston moves from bottom to top, no heat transfer, Temp up, Pressure up, Volume down
  2. Reversible Isochoric Heating (2 to 3): Piston at top, Ignition of fuel/air mix, temp up, Pressure up, volume constant
  3. Adiabatic Expansion (3 to 4): High Pressure Forces Piston down, temp down, no heat transfer
  4. Reversible Isochoric rejection (cooling) (4 to 1): Piston is at bottom, Pressure and temp decrease to initial levels
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99
Q

Phases skipped by Otto cycle (Piston engines)

A

-INDUCTION and EXHAUST phases
-Due to WORKING FLUID being CONSTANTLY REUSED

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100
Q

3 components required for Brayton cycle (gas turbine engines)

A
  1. Gas Compressor
  2. Mixing Chamber (Combustion Chamber)
  3. Expander (Turbine)
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101
Q

4 Processes of Brayton cycle (gas turbine engines)

A
  1. Adiabatic Compression (1 to 2): Fresh Air into compressor, No heat transfer, temp up, Pressure up, volume down
  2. Isobaric Heating (2 to 3): compressed air into combustion chamber, fuel burned to heat air, pressure constant, temp up, volume up
  3. Adiabatic Expansion (3 to 4): Air gives up energy as it expands through the turbine, some turbine work drives compressor, pressure down, temp down, no heat transfer
  4. Isobaric Cooling (4 to 1): Air cools in atmosphere, volume and temp down to Initial levels
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102
Q

Constant volume process

A

-ISOCHORIC
-considered REVERSIBLE in a PERFECT GAS
-working fluid kept in RIGID CONTAINER
-system boundaries are IMMOVABLE, no work can be done on or by the system
-all heat supplied increases INTERNAL ENERGY of the WORKING FLUID
-eg BRAYTON CYCLE

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103
Q

Constant pressure process

A

-ISOBARIC
-REVERSIBLE process for a PERFECT GAS
-boundary of system NOT RIGID
-to keep CONSTANT PRESSURE, VOLUME must CHANGE
-boundary moves against EXTERNAL RESISTANCE as HEAT is supplied
-WORK is done by fluid onto its SURROUNDINGS

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104
Q

Latent Heat

A

-Heat absorbed or released during CONSTANT TEMPERATURE (ISOTHERMIC) Process

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105
Q

Latent Heat of Fusion

A

-Heat added causing solid to liquid state change
-eg when ice melts at 0 degrees Celsius, water and ice remain at 0 degrees until state change is COMPLETE

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106
Q

Latent Heat of Evaporation

A

-Heat added causing Liquid to Gas state change
-eg Boiling water at 100 degrees Celsius, steam and water remain at 100 degrees until state change is COMPLETE

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107
Q

Thermal Energy

A

-KINETIC ENERGY possessed by an object due to particles moving within it
-Allows for TEMPERATURE to be measurable
-Is the ability to do WORK

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108
Q

Heat of Combustion

A

-ENERGY releases as HEAT during COMPLETE COMBUSTION with OXYGEN
-Usually from hydrocarbon/organic molecule combusting
-CO2 and Water also released
-Heat level varies based off compound of FUEL

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109
Q

Light

A

-ELECTROMAGNETIC RADIATION visible to the human eye

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110
Q

Electromagnetic Waves

A

-MAGNETIC and ELECTRIC field travelling together
-Fields are DISPLACED at 90 DEGREES to each other
-Follow a SINUSOIDAL pattern (forming SINE WAVES)

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111
Q

Colour of Light

A

-Different FREQUENCIES or WAVELENGTHS of ELECTROMAGNETIC WAVES hitting the retina
-HIGH Frequency = BLUER until ULTRA-VIOLET
-LOW Frequency = REDDER until INFRA-RED

112
Q

2 units to measure Light wavelengths

A
  1. Nanometres
  2. Angstroms

1 Angstrom = 0.1 Nanometres

113
Q

Visible Light Range

A

-Range of 400-700 Nanometres
-X-rays and other equipment used to detect ELECTROMAGNETIC RADIATION outside this range

114
Q

Speed of Light in a vacuum

A

-300,000,000 m/s
-3x10^8 m/s

115
Q

If speed of light is not given

A

-Assume it is travelling through a vacuum
-3x10^8 m/s
-300,000,000 m/s

116
Q

Reflection at Plane surface

A

-Angle of INCIDENCE is EQUAL to angle of REFLECTION
-NORMAL is PERPENDICULAR to the surface
-Incident Ray, reflected Ray and Normal are all in the SAME PLANE

117
Q

Real image

A

-Can be PROJECTED onto a screen/wall

118
Q

Virtual Image

A

-Can only be seen by LOOKING INTO OPTICS
-Light rays are perceived as originating from elsewhere
-eg perceiving mirror reflection as behind the mirror

119
Q

Images formed in Plane mirrors

A

-Same size as object
-Percieved as same distance behind mirror as object is from from of mirror
-VIRTUAL
-LATERALLY INVERTED (text appears backwards)

120
Q

Convex mirror

A

-Curves OUTWARDS
-Reflected rays DIVERGE
-Image appears SMALLER
-Reflection has WIDE FOV

121
Q

Concave Mirror

A

-Curves INWARDS
-Reflected rays CONVERGE
-close up image = MAGNIFIED, UPRIGHT and VIRTUAL
-far away image = DIMINISHED, INVERTED and REAL
-eg magnified views in technology

122
Q

Refraction

A

-CHANGE in DIRECTION of a WAVE when it enters a DIFFERENT MEDIUM
-Some Light REFLECTED back into first medium
-Direction change caused by change in SPEED OF LIGHT
-If Light is PERPENDICULAR to the surface it changes speed but NOT DIRECTION

123
Q

Refractive Index

A

-Ratio of speed of light in VACUUM (3x10^8m/s) to speed of light in MATERIAL
-HIGH REFRACTIVE INDEX = More light bending, SLOWER speed of Light

124
Q

Snell’s Law

A

-Describes relationship between ANGLE OF INCIDENCE and ANGLE OF REFRACTION.
-Used to determine REFRACTIVE INDEX of materials

125
Q

Convex Lens

A

-CONVERGING Lens
-Curves OUTWARDS on BOTH SIDES
-May form REAL or VIRTUAL image depending on POSITION in relation to Lens
-eg Magnifying glasses, cameras and naturally in the EYE

126
Q

Concave Lens

A

-DIVERGING Lens
-Curves INWARDS on BOTH SIDES
-Image formed is always UPRIGHT, VIRTUAL and DIMINISHED
-eg Spectacles, binoculars and Telescopes

127
Q

Fibre optics

A

-DATA INFORMATION covered to a LIGHT SIGNAL travels through fibre cables

128
Q

3 Advantages of Fibre optic cables

A
  1. Light and Small
  2. Carry more information
  3. Safer (no fire risk)
129
Q

2 Disadvantages of Fibre optic cables

A
  1. Difficult to Terminate
  2. Difficult to repair (Fibres thinner than human hair)
130
Q

2 components of a fibre optic strand and their function

A
  1. High refractive index Core
  2. Low refractive index Cladding

-Light reflects off Cladding, remaining in Core, resulting in TOTAL INTERNAL REFLECTION and reducing signal loss over long distances

131
Q

Mechanical Waves

A

-OSCILLATION of MATTER, requires MEDIUM to transmit ENERGY through
-eg Sound Waves (need Air molecules to exist)

132
Q

2 types of Mechanical Wave

A
  1. Transverse
  2. Longitudinal
133
Q

Transverse Mechanical wave

A

-Displacement of MEDIUM is PERPENDICULAR to direction of PROPAGATION of the WAVE

134
Q

Longitudinal Mechanical wave

A

-Displacement of MEDIUM is PARALLEL to direction of PROPAGATION of the WAVE
-eg Sound waves

135
Q

Sine Waves

A

-Have a PERIODIC WAVEFORM
-Repeat at a STANDARD INTERVAL
-Repeat in a SPECIFIC MANNER
-Have a CONSTANT AMPLITUDE

136
Q

Amplitude of a Waveform

A

-Greatest Displacement from REST POSITION
-ie Peaks and Troughs of waves

137
Q

Wavelength

A

-Distance from one point on wave to next point at SIMILAR POSITION
-eg PEAK to PEAK

138
Q

Periodic time of waveforms

A

-Time taken to complete ONE OSCILLATION

139
Q

Frequency of Waveform

A

-Number of COMPLETED OSCILLATIONS per SECOND

140
Q

Which 2 waveform properties are Reciprocals of eachother? (Dividing 1 by one of them gives h value of the other)

A

-Periodic Time and Frequency

141
Q

Interference Phenomena

A

-Formation of a RESULTANT WAVE of a DIFFERENT AMPLITUDE when 2 waves travelling through the SAME MEDIUM meet.

142
Q

What is the Amplitude of the resultant wave when 2 sine waves of identical amplitude travelling towards eachother through the same medium meet?

A

-Double the Amplitude of one of the sine waves

143
Q

Standing wave

A

-Combination of 2 waves of SAME AMPLITUDE and FREQUENCY moving in OPPOSITE DIRECTIONS
-Combination OSCILLATES in TIME but its PEAK AMPLITUDE PROFILE doesn’t move in SPACE

144
Q

Progressive Waves

A

-Waves that move NORMALLY

145
Q

Sound Waves

A

-VIBRATIONS through AIR or OTHER MEDIUM that can be detected by ELASTIC MEDIUM such as EAR DRUMS

146
Q

Speed of Sound in room temperature air

A

343 m/s

147
Q

Speed of sound in water

A

1500 m/s

148
Q

Speed of sound in Bar of Steel

A

5000m/s

149
Q

Mach Number

A

-Describes ratio of AIRCRAFT SPEED in relation to SPEED OF SOUND
-Aircraft speed/Speed of sound = Mach Number

150
Q

2 Factors Loudness depends on

A
  1. AMPLITUDE of Vibrations
  2. DISTANCE from the SOUND SOURCE
151
Q

Compression of Sound waves

A

-Areas of DENSE air cause LONGITUDINAL Sound waves to COMPRESS

152
Q

Sound Intensity

A

-aka AMPLITUDE
-Expressed in terms of PRESSURE
-Quantified using LOGARITHMIC DECIBEL AMPLITUDE SCALE

153
Q

Quietest Sound humans can hear

A

0 decibels

154
Q

Sound intensity that cause damage with Prolonged exposure

A

85 decibels

155
Q

Sound intensity that causes severe pain and permanent damage

A

130 decibels or higher
-eg jet engine

156
Q

Unit of Sound Pressure Level (SPL)

A

-Decibels

157
Q

Pitch of Sound

A

-Determines how SHRILL or DEEP sound is
-Determined by FREQUENCY
-High Frequency = High Pitch

158
Q

Pitch of Tone

A

-Proportional to Number of COMPRESSIONS and RAREFACTIONS received PER SECOND
-Determined by VIBRATION FREQUENCY of the SOUND SOURCE

159
Q

Quality of sound

A

-Used to distinguish between 2 sounds with SAME PITCH AND LOUDNESS
-eg 2 instruments of the same type
-Determined by variations in number and Intensity of OVERTONES
-Allows recognition of different HUMAN VOICES

160
Q

Fundamental Frequency

A

-LOWEST Frequency tone produced

161
Q

Overtones or Harmonics

A

-Other tones of higher frequency than FUNDAMENTAL FREQUENCY
-Used to Determined QUALITY OF SOUND

162
Q

Doppler Effect

A

-Percieved pitch of Sound (such as siren) getting lower as it moves past you
-Present for all wave motion
-Moving Towards = SHORTER WAVELENGTHS, HIGHER PITCH
-Moving Away = LONGER WAVELENGTHS, LOWER PITCH

163
Q

Viscosity

A

-RESISTANCE of a Fluid to change its shape
-OPPOSITION to FLOW

164
Q

Liquid Viscosity

A

-DECREASES RAPIDLY as TEMPERATURE INCREASES

165
Q

Gas Viscocity

A

-INCREASES as TEMPERATURE INCREASES

166
Q

Fluid Resistance

A

-aka Fluid friction
-Occurs when Solids travels through liquid or gas
-eg WIND RESISTANCE

167
Q

3 Factors effecting Fluid Resistance

A
  1. VISCOSITY of Fluid
  2. TEXTURE of Solid object
  3. SHAPE of Solid object
168
Q

Streamlining

A

-Decreasing amount of RESTRICTIVE FORCE from FLUID RESISTANCE
-eg Countersunk rivets or use of composites on Aircraft skin

169
Q

If a Liquid is Compressable

A

-INCREASED PRESSURE = INCREASED INTERNAL TEMPERATURE
-INCREASED PRESSURE = REDUCED VISCOSITY

170
Q

If a Gas is compressable

A

-INCREASED PRESSURE = INCREASED VISCOCITY

171
Q

Fluid Pressure

A

-Determined by height of column of Liquid and type of Liquid
-More height = MORE PRESSURE
-Measuring halfway up column = LOWER PRESSURE

172
Q

Pascal’s Law

A

-When PRESSURE is applied to a CONTAINED LIQUID, the liquid exerts an EQUAL PRESSURE at RIGHT ANGLES to the container

173
Q

Static Pressure

A

-Exists IN ADDITION to any DYNAMIC FACTORS also present
-PASCAL’S LAW applies to Static Pressure

174
Q

Dynamic pressure

A

-Formed as a result of the VELOCITY of a Fluid in MOTION

175
Q

Total Pressure

A

-Sum of STATIC PRESSURE and DYNAMIC PRESSURE

176
Q

Bernoulli’s Theorem

A

-POTENTIAL ENERGY and PRESSURE decrease when KINETIC ENERGY or VELOCITY Increase

177
Q

Potential Energy in Fluids

A

-Result of FLUID PRESSURE

178
Q

Venturi Tube

A

-Narrower In middle than at ends
-Has Higher Velocity and Kinetic energy in the central restriction but lower Pressure and Potential energy
-TOTAL EMERGY REMAINS THE SAME
-Used In gyroscopic Aircraft instruments

179
Q

Temperature

A

-Measure of AVERAGE KINETIC ENERGY of particles
-Warmer = FASTER
-Property of system that determines if it is in THERMAL EQUILIBRIUM

180
Q

Heat flow

A

-Transfer of Heat from HOTTER to COLDER body
-Usually occurs naturally until THERMAL EQUILIBRIUM is reached

181
Q

3 types of Thermometer

A
  1. Bulb (standard)
  2. Bimetallic
  3. Thermistor
182
Q

Thermocouples

A

-Used to measure HIGH TEMPERATURES
-eg Measures EGT In Gas turbine Engines

183
Q

Bulb Thermometer

A

-Contains Fluid such as Mercury
-Reads Temperature via FLUID EXPANSION
-Water Not Used As it will FREEZE/BOIL

184
Q

Bimetallic Thermometer

A

-Shows Temperature via MECHANICAL DISPLACEMENT
-Functions via 2 different metals EXPANDING at different rates as they heat up
-Often Used In HEAT SENSORS or to read Free air temp and outside air temp in light aircraft

185
Q

Thermistors

A

-THERMAL RESISTORS
-Most commonly used SENSOR
-COMPUTER measures RESISTANCE of material and converts it to a TEMPERATURE reading

186
Q

Freezing point of Water in Fahrenheit

A

32 degrees Fahrenheit

187
Q

Boiling point of Water in Fahrenheit

A

212 degrees Fahrenheit

188
Q

Temperature at which Celsius and Fahrenheit read the same

A

-40 degrees

189
Q

Kelvin

A

-Base unit of TEMPERATURE in SI UNITS
-0 Kelvin = ABSOLUTE ZERO

190
Q

Absolute Zero

A

-Temperature at which all molecular movement CEASES
-Cannot actually be reached
-Classed as a LIMITING TEMPERATURE

191
Q

Absolute Zero in Celsius

A

-273.15 degrees Celsius

192
Q

Absolute Zero in Fahrenheit

A

-460 degrees Fahrenheit

193
Q

calorie/Calorie

A

-calorie is ONE THOUSANDTH of a Calorie (CAPITAL C)
-Used to measure HEAT ENERGY in FOOD

194
Q

What is required to move heat in reverse from a lower temperature body to a higher temperature body?

A

-WORK

195
Q

3 methods of heat energy transfer

A
  1. Conduction
  2. Convection
  3. Radiation (works in empty space)
196
Q

Specific heat

A

-Amount of Heat needed to raise Temperature of 1kg of material by 1 degree Celsius

197
Q

Heat capacity

A

-aka Thermal mass
-Ratio of HEAT ENERGY transferred to resulting TEMPERATURE increase
-Measurement of capability of a substance to ABSORB HEAT ENERGY

198
Q

Heat Transfer

A

-Flow of Heat due to TEMPERATURE DIFFERENCES
-Subsequent TEMPERATURE CHANGES and DISTRIBUTION

199
Q

Conduction

A

-Occurs in SOLIDS and FLUIDS
-Heat DIRECTLY TRANSFERRED through MATERIAL
-Atom and molecule VIBRATION carries energy

200
Q

Convection

A

-FLUIDS ONLY
-Heat transfer from ONE PART OF FLUID TO ANOTHER
-eg Heat rising

201
Q

Thermal Radiation

A

-Most efficient through a VACUUM
-Temperature INCREASE = AMOUNT and PEAK FREQUENCY of radiation INCREASES (eg iron going red to white hot)
-Substances DONT need to be in contact with eachother to transfer heat via radiation (eg SUN heating Earth)

202
Q

Thermal Expansion/Contraction

A

-EXPAND when HEATED
-CONTRACT when COOLED
-HEAT = Molecule VIBRATION = Bigger gaps between molecules = EXPANSION

203
Q

Coefficient of linear thermal expansion

A

1 degree Celsius

204
Q

Linear Expansion

A

-Length changes by amount PROPORTIONAL to ORIGINAL LENGTH and CHANGE IN TEMPERATURE

205
Q

Area Expansion

A

-Experienced by TWO-DIMENSIONAL SOLID BODIES
-WIDTH and HEIGHT change in MAGNITUDE

206
Q

Volumetric Expansion

A

-HEIGHT, WIDTH and DEPTH change in MAGNITUDE

207
Q

Matter states in order of Most to least thermal Expansion

A
  1. Gases - Most room for molecules to VIBRATE APART
  2. Liquids
  3. Solids
208
Q

First Law of Thermodynamics

A

-ENERGY cannot be CREATED or DESTROYED, only TRANSFORMED
-Energy In = Energy Out

209
Q

Second Law of Thermodynamics

A

-The total ENERGY output provided by a MACHINE is equal to the amount of HEAT applied, some energy is WASTED
-HEAT supplied must be GREATER than WORK done by MACHINE

210
Q

Entropy

A

-IRREVOCABLE loss of ENERGY to the ENVIRONMENT due to DISORDER in the system
-TOTAL ENTROPY in the Universe can only INCREASE or REMAIN THE SAME

211
Q

Two types of Thermodynamic Cycles

A
  1. OPEN
  2. CLOSED
212
Q

5 Basic elements of a Thermodynamic cycle

A
  1. Working substance (eg Oil)
  2. Heat source
  3. Heat reciever
  4. Pump
  5. Engine (converts THERMAL ENERGY into WORK)
213
Q

Open cycles

A

-OPENING in system BOUNDARY
-WORKING FLUID can be REGULARLY REPLACED
-Fluid TAKEN in and DISCARDED after each CYCLE
-eg Gas turbine engines

214
Q

Closed cycles

A

-FIXED BOUNDARY containing FIXED AMOUNT of VAPOUR/GAS
-Fluid returns to INITIAL STATE after each CYCLE
-NO MASS TRANSFER
-Interchange of HEAT and WORK occurs
-eg Refrigerator

215
Q

Ideal Gas

A

-Gas shown through experiments to adhere closely to IDEAL GAS LAWS
-eg Hydrogen, Oxygen, Nitrogen

216
Q

Boyle’s Law

A

-ISOTHERMAL PROCESS
-At a CONSTANT TEMPERATURE, the PRESSURE exerted by a Gas varies INVERSELY with the VOLUME
-eg SMALLER VOLUME = HIGHER PRESSURE

217
Q

Charles’ Law

A

-ISOBARIC PROCESS
-At a CONSTANT PRESSURE, the VOLUME of Ideal gas INCREASES in DIRECT PROPORTION to the TEMPERATURE INCREASE
-eg Higher Temperature = Bigger Volume

218
Q

Gay-Lussac’s Law

A

-ISOCHORIC PROCESS
-At a CONSTANT VOLUME, the PRESSURE of Gas is DIRECTLY PROPORTIONATE to the ABSOLUTE TEMPERATURE

219
Q

Specific heat at constant volume

A

-ISOCHORIC PROCESS
-No WORK is done
-Heat supplied only changes THERMAL ENERGY

220
Q

Density

A

-How tightly particles are packed in a material (MASS per UNIT VOLUME)
-Liquids and solids have similar density
-Gases have MUCH LOWER density
-Density varies between materials

221
Q

Specific Gravity

A

-aka RELATIVE DENSITY
-Used to compare density of 2 substances
-Is a RATIO and has NO UNIT

222
Q

What are all Liquids and Solids compared to in regards to Specific Gravity?

A

-Water At 4 degrees Celsius

223
Q

What are all gases compared to in regards to Specific Gravity?

A

-Air At room temperature (20 degrees Celsius)

224
Q

Hydrometer

A

-Used to measure SPECIFIC GRAVITY of LIQUIDS
-Glass float within larger glass tube filled with test liquid
-Float is weighted and has VERTICAL SCALE which can be read off the SURFACE of the test liquid

225
Q

Pure Water Hydrometer reading

A

-1000
-Specific Gravity = 1

226
Q

Charged Battery Electrolyte Hydrometer reading

A

-1275 to 1310
-SPECIFIC GRAVITY = 1.275-1.31

227
Q

Discharged battery electrolyte Hydrometer reading

A

-1150
-Specific Gravity = 1.15

228
Q

Harmonic Series

A

-1st Harmonic = The FUNDAMENTAL
-2nd Harmonic = 1st OVERTONE
-3rd Harmonic = 2nd OVERTONE
-etc

229
Q

Resonance

A

-Tendency for system to oscillate at its MAXIMUM AMPLITUDE when at its RESONANT FREQUENCY

230
Q

Velocity Ratio

A

-How far EFFORT has to move in relation to LOAD
-Has NO UNIT
-If Velocity Ratio is GREATER THAN 1, then the distance moved by the POINT OF EFFORT is greater than the distance moved by the LOAD

231
Q

Mechanical Advantage

A

-RATIO of FORCE PRODUCED in relation to FORCE APPLIED
-Has NO UNIT

232
Q

Actual Mechanical Advantage

A

-RATIO of OUTPUT FORCE in relation to INPUT FORCE
-Has NO UNIT

233
Q

Ideal Mechanical Advantage

A

-RATIO of INPUT DISTANCE in relation to OUTPUT DISTANCE
-Represents Mechanical Advantage that would exist with NO FRICTION in the MACHINE

234
Q

Inclined Plane

A

-SURFACE inclined at any angle EXCEPT RIGHT ANGLE
-Allows LARGE RESISTANCE to move a long distance with LESS EFFORT

235
Q

Single, fixed pulley

A

-IDENTICAL to FIRST CLASS LEVER
-MECHANICAL ADVANTAGE = 1

236
Q

Single, moving pulley

A

-Moves in same direction as WEIGHT
-IDENTICAL to SECOND CLASS LEVER
-MECHANICAL ADVANTAGE = 2
-eg Input Force of 50N = Output Force of 100N

237
Q

Calculating combined Pulley Mechanical Advantage

A

-Count the ropes acting on the MOVING PULLEY

238
Q

Calculating combined pulley rope length

A

-Multiply MECHANICAL ADVANTAGE by DESIRED MOVEMENT

239
Q

Mechanical advantage in gears

A

-Depends on NUMBER OF TEETH
-If same number of teeth, MA = 1
-If DRIVEN gear has twice the teeth of DRIVE gear, MA = 2 etc

240
Q

Gear Ratio

A

-Ratio of Driven gear teeth:Drive gear teeth
-Simplify if possible (eg 16:8 to 2:1)

241
Q

Revolution Ratio

A

-OPPOSITE OF GEAR RATIO
-Ratio of Drive Gear teeth:Driven gear teeth

242
Q

Spur Gears

A

-Teeth cut STRAIGHT ACROSS circumference
-connect 2 PARALLEL shafts
-If both have EXTERNAL teeth, shafts turn OPPOSITE directions
-If one has INTERNAL teeth, shafts turn SAME direction

243
Q

Bevel Gears

A

-Teeth cut into comical surface known as PITCH ZONE
-Connects two shafts at AN ANGLE to eachother
-Used when drive and driven shafts are NOT PARALLEL
-Teeth are always EXTERNAL, shafts turn OPPOSITE directions
-Angle Usually 90 degrees but can be up to 180

244
Q

Worm gears

A

-Toothed wheel driven by revolving WORM CYLINDER
-Worm has SCREW THREAD
-Used for large REDUCTION SPEED and HIGH TORQUE MULTIPLICATION applications

245
Q

Sun and Planet Gears

A

-SUN gear with INPUT DRIVE
-PLANET gears held by CAGE and rotate around SUN gear and FIXED OUTER RING GEAR
-OUTPUT comes from CAGE which rotates in SAME DIRECTION as SUN gear but rotates SLOWER
-Used for LARGE SPEED REDUCTION and HIGH TORQUE applications

246
Q

Efficiency

A

-RATIO of WORK transferred to USEFUL FORM vs TOTAL INPUT WORK
-Expressed as a PERCENTAGE

247
Q

Newton’s Second Law

A

-The ACCELERATION of an object produced by a FORCE is DIRECTLY PROPORTIONAL to the FORCE, is in the SAME DIRECTION as the FORCE, and is INVERSELY PROPORTIONAL to the MASS of the object
-F = m x a

248
Q

Gravitational Acceleration

A

9.81 m/s^2

249
Q

Newton’s Third Law

A

-Every ACTION has an EQUAL AND OPPOSITE REACTION

250
Q

Mass

A

-Amount of MATTER in a body regardless of VOLUME or POSITION

251
Q

What is 1kg In Amu?

A

6.02x10^26Amu

252
Q

Weight

A

-GRAVITATIONAL FORCE of ATTRACTION between MASS OF EARTH and the MASS OF A BODY
-DECREASES as body moves AWAY from EARTHS CENTRE

253
Q

What does a 750N body at the North Pole weigh at the Equator?

A

745N

254
Q

Inertia

A

-RESISTANCE to change in STATE OF REST or MOTION triggered by a FORCE
-Greater MASS = Greater INERTIA

255
Q

Work

A

-FORCE causing MOVEMENT or DISPLACEMENT
-Increased FORCE = Increased WORK
-Increased DISTANCE MOVED = Increased WORK

256
Q

Power

A

-RATE at which WORK is done over TIME
-Measured in Watts(W), horsepower(hp) or metric horsepower (PS)

257
Q

Mechanical Energy

A

-ENERGY held by a body after WORK has been done
-Combination of KINETIC and POTENTIAL energy

258
Q

Potential Energy

A

-ENERGY body holds due to POSITION/CONDITION (does WORK when released)

259
Q

Gravitational Potential Energy

A

-Form of POTENTIAL ENERGY that INCREASES as a body is LIFTED
-Dependant on GRAVITATIONAL ACCELERATION (9.81m/s^2), MASS and HEIGHT

260
Q

Kinetic Energy

A

-ENERGY body has due to MOTION
-Faster MOTION = higher KINETIC ENERGY
-Object AT REST has NO KINETIC ENERGY
-Depends on MASS and VELOCITY

261
Q

Total Energy

A

-SUM of ALL ENERGY in a system
-Energy Cannot be CREATED or DESTROYED
-Energy CHANGES FORM but TOTAL ENERGY remains THE SAME

262
Q

Chemical Energy

A

-ENERGY stored in the CHEMICAL BONDS between ATOMS
-Released or consumed via CHEMICAL REACTION (BONDS changing)
-Is a form of POTENTIAL ENERGY

263
Q

Momentum

A

-VECTOR QUANTITY describing MASS in MOTION
-Depends on MASS and VELOCITY
-More MASS or VELOCITY = more MOMENTUM
-Direction of MOMENTUM same as direction of VELOCITY

264
Q

Momentum in a closed system

A

-Total momentum before event = total momentum after event

265
Q

Collision

A

-Two bodies INTERACT, transferring KINETIC ENERGY and MOMENTUM
-Total MOMENTUM always CONSERVED
-Total KINETIC ENERGY may CHANGE

266
Q

2 Types of Collision

A
  1. ELASTIC: Kinetic Energy CONSERVED, No HEAT or DEFORMATION
  2. INELASTIC: Kinetic Energy CHANGES, HEAT and DAMAGE occur
267
Q

Impulse

A

-VECTOR quantity
-IMPULSE of a FORCE changes the MOMENTUM of a body
-Equal to FORCE multiplied by the TIME the FORCE acts on the body

268
Q

2 Vital gyroscopic principles

A
  1. RIGIDITY
  2. PRECESSION
269
Q

Rigidity

A

-RETAINS SPIN AXIS unless acted on by an EXTERNAL FORCE
-Caused by INERTIA
-aka Gyroscopic Inertia

270
Q

4 factors affecting Rigidity/Gyroscopic Inertia

A
  1. Rotor Mass
  2. Effective radius at which mass acts
  3. Speed of rotation
  4. Bearing friction
271
Q

Precession

A

-RESISTS attempts of EXTERNAL FORCE to change DIRECTION of ROTOR SPIN AXIS
-Moves FORCE at RIGHT ANGLES to ORIGINAL APPLIED DIRECTION

272
Q

Starting Friction

A

-aka STATIC FRICTION/BREAK-AWAY FORCE
-Present when RESTING BODY begins to MOVE
-Amount depends on nature of MATERIAL SURFACES

273
Q

Sliding Friction

A

-Present As body SLIDES over another surface
-Always LESS than STARTING FRICTION
-Present In bodies ALREADY IN MOTION
-Amount depends on NATURE OF MATERIAL SURFACES

274
Q

Rolling Friction

A

-Present between ROLLING BODY and the surface it ROLLS over
-MUCH SMALLER than SLIDING FRICTION (Less RESISTANCE)

275
Q

Coefficient of Friction

A

-Every PAIR of FLAT SURFACES have 2 DIFFERENT coefficients of friction
-STARTING FRICTION = greatest coefficient
-SLIDING FRICTION = smaller coefficient
-ROLLING FRICTION = smallest coefficient

DHL Physics (3 decks)

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