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B1 2-physics > Mechanics > Flashcards

Mechanics Flashcards

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1
Q

What is Newton’s first law of motion?

A

A body will remain at rest or continue to move with a uniform velocity unless acted upon by a force

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2
Q

What is the metric system unit of force?

A

Newtons

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3
Q

What is the imperial system for force?

A

Pounds

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4
Q

What is the equation of force?

A

Force= mass x acceleration

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5
Q

What is a moment?

A

A turning effect produced by a force

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6
Q

What is another way to describe mechanical advantage?

A

A moment

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7
Q

What is the equation for a moment?

A

Moment= force x perpendicular distance

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8
Q

What is the definition of a fulcrum?

A

The point at which you pivot against/around

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9
Q

What is a couple?

A

A pair of forces that are equal in magnitude and different in direction i.e when a aircraft rolls the forces on both ends of wings one is up and one is down

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10
Q

What is a resultant force?

A

The effect that results from two or more vectors acting on an object i.e two people pushing a box at 500N and 330N is a resultant of 880N

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11
Q

When would you use the triangle method (Pythagoras) to work out a resultant force?

A

When you have two forces acting with a 90° angle

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12
Q

What theorem does the triangle method use?

A

Pythagoras theorem

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13
Q

What is a scalar?

A

Are quantities that have magnitude but no direction i.e length, distance, speed

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14
Q

What is a vector?

A

They have a magnitude as well as direction in a straight line i.e velocity, acceleration, force and momentum

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15
Q

What is the abbreviation CG stand for?

A

Centre of gravity

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16
Q

What is the force of gravitational pull?

A

9.8 per m/s^2

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17
Q

When choosing a datum for the aircraft what is the only fixed rule to follow?

A

The datum must be positioned in a location that will not change during the life of the aircraft

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18
Q

How would you find the CG of an aircraft?

A

You would calculate the moments affecting all landing gear and add them together then simplify to get a distance

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19
Q

What happens to an aircraft before it leaves the production line?

A

It goes under structural testing

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20
Q

What is the definition of stress?

A

A quantity that describes the magnitude of forces that cause deformation

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21
Q

What is deformation also known as?

A

Strain

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22
Q

Stress is always accompanied by?

A

Strain

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23
Q

What is the unit for stress in the metric system?

A

Pascal or N/m^2

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24
Q

What is the unit for stress in the imperial system?

A

Pounds per square inch (Psi)

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25
Q

What is the equation for stress?

A

Force over area

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26
Q

What are the five basic structural stresses?

A

-tension
-compression
-shear
-bending
-torsion

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27
Q

What is the definition of strain?

A

The deformation of a material due to stress

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28
Q

Why does strain have no units?

A

Because its a ratio

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29
Q

What is the calculation for strain?

A

Change in length over original length

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30
Q

What is elasticity?

A

The ability of a material to return to its original shape once external forces are removed

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31
Q

What is the opposite to elasticity?

A

Plasticity

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32
Q

what is plasticity?

A

The ability of a material to change its shape permanently when its subjected to stress

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33
Q

What is tension?

A

When stress being applied tends to increase the length of the body

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34
Q

What is tension also known as?

A

-tensile stress
-axial stress
-normal stress

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35
Q

What is hooke’s law?

A

The extension of an elastic object is directionally proportional to the force applied to it

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36
Q

When does hooke’s law work?

A

When the elastic limit has not be exceeded

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37
Q

What is the elastic limit?

A

The point at which permanent deformation occurs and the elastic region ends

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38
Q

Once a material goes past the elastic limit what region does it enter?

A

The plastic region

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39
Q

When in the plastic region what becomes inproportional?

A

The force and deformation i.e small force means big deformation

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40
Q

What is compression?

A

The force which tends to shorten or squeeze a body

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41
Q

What is compression strength measured in?

A

N/m^2

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42
Q

What is shear stress?

A

When a body is being sliced by sliding one layer over another

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43
Q

What bolt is used to withstand shear loads?

A

Clevis bolts

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44
Q

What is bending?

A

When one side is under tension and the other side is being compressed

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45
Q

What is torsional stress?

A

When a material is being twisted

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46
Q

What two stress are found when a material is under torsion?

A

Tension and compression

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47
Q

At what angle does tension and compression work at when a material is under torsion?

A

Diagonally across the object

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48
Q

What is the definition of hardness?

A

The tendency to resist indentation or penetration of its surface i.e diamonds

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49
Q

What is the definition of strength?

A

The ability to withstand load without failure or plastic deformation i.e steel or titanium

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50
Q

What is the definition of toughness?

A

The tendency to resist breakage when deforming or when impact forces are applied i.e a hammer head or overcooked meat

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51
Q

What is brittleness?

A

The tendency to break without changing shape i.e glass or concrete

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52
Q

When do most materials get more brittle?

A

When cooled

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53
Q

What is elasticity?

A

The ability to return to its original shape when the force is removed i.e rubber bands

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54
Q

What is plasticity?

A

The tendency to remain in the new shape when the distorting force is removed i.e wet clay or play dough

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55
Q

What is the definition of malleability?

A

The ability to undergo compressive stress without damage i.e red hot steel

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56
Q

What is ductility?

A

The tendency to undergo tensile stress without damage i.e copper wire

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57
Q

What is the definition of fluid?

A

Any substance that flows (such as liquid, gases, and vapours)

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58
Q

What is the definition of vapour?

A

A gas that can be liquified by an increase in pressure without decreasing its temperature

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59
Q

What is the name for a gas when its below its boiling point?

A

A vapour

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60
Q

What is a volatile liquid?

A

When it readily evaporates at normal temperature with space above the surface

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61
Q

If you had a volatile liquid in a container with a open top, what would happen to the liquid?

A

It would evaporate until the liquid is gone

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62
Q

What is flammability?

A

When a material will catch on fire easily

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63
Q

Vapours given off by volatile liquids are?

A

Highly flammable

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64
Q

Flammable and inflammable are synonyms but which is preferred?

A

Flammable

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65
Q

What is flash point?

A

The temperature at which something will catch fire when exposed to a naked flame

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66
Q

When a substance has a lower flash point is it easier or harder to ignite the material?

A

Easier

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67
Q

What is toxicity of substance?

A

It refers to how poisonous it is

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68
Q

Common signs of being around toxic substances?

A

Skin irritations, soreness in the eyes, feeling sick, and difficulty in breathing

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69
Q

What is the definition of inert?

A

Any substance that will not chemically combine with another substance

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70
Q

All inert substances are?

A

Gases

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71
Q

What is the calculation for pressure?

A

Pressure = force over area

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72
Q

How do you calculate area?

A

πr^2

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73
Q

What is atmospheric pressure?

A

The force exerted by the weight of the atmosphere

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74
Q

The density of air varies when what change?

A

Altitude

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75
Q

At sea level what is the average atmospheric pressure?

A

14.7psi

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76
Q

What is the most common barometer?

A

Mercury barometer

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77
Q

What is used to measure atmospheric pressure?

A

Barometers

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78
Q

If atmospheric pressure is 14.7 psi what is it in bar?

A

1.01 bar

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79
Q

How does. Mercury barometer work?

A

A vertical glass tube is placed sitting on top of a mercury bath and when the pressure increase more mercury is sucked up

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80
Q

What is gauge pressure?

A

The difference between the pressure inside a body and the pressure outside

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81
Q

What is absolute pressure?

A

The difference between the pressure inside a body and zero pressure

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82
Q

What is archimedes principle on buoyancy?

A

That a body in a fluid will be subject to an upward force equal to the weight of fluid it displaces

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83
Q

When does neutral buoyancy occur?

A

When an objects weight is equal to the weight of the fluid displaced

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84
Q

What are the 3 simple stresses?

A

-tension
-compression
-shear

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85
Q

What is the definition of a combined stress ?

A

When an object is affected by more than one type of stress at a time

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86
Q

What is motion?

A

A continuing change of position

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87
Q

If a object is in motion and if the distance the object moves remains the same it is said to be?

A

Uniform

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88
Q

What is velocity?

A

The change in displacement over time

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89
Q

If a objects velocity is not constant, it is said to be?

A

Accelerating

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90
Q

What is the equation for acceleration?

A

Change in velocity over time

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91
Q

Why is velocity a vector quantity?

A

Because it has a direction

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92
Q

Why is speed a scalar quantity?

A

Because it doesn’t have a direction

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93
Q

If there is two objects traveling at 10m/s in opposite directions have the same speed But different?

A

Velocities

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94
Q

Why is it possible for an object to change in acceleration but not speed?

A

Because acceleration is the change of speed, direction, or both

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95
Q

How do you calculate acceleration?

A

(Initial velocity^2 minus final velocity^2) over 2 times displacement

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96
Q

When is the only time acceleration remains constant?

A

When the acceleration is caused by earths gravitational pull

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97
Q

If a stone is dropped from a tower and takes 4 seconds to reach the ground, what is the velocity at impact?

A

Initial+gravity x time
0+9.8 x 4 =39.2

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98
Q

If a satellite is orbiting earth at a constant speed, is its velocity changing?

A

Yes because its changing direction constantly

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99
Q

What is centripetal force?

A

The force required to cause acceleration towards the centre of rotation

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100
Q

What is Newton’s first law?

A

An object at rest remains at rest, and an object in motion remains in motion unless acted on by an unbalanced force

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101
Q

What is the equation for centripetal force?

A

Mass x velocity^2 over radius

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102
Q

What is centripetal acceleration?

A

The acceleration experienced while in uniform circular motion

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103
Q

What direction does centripetal acceleration act?

A

Towards the centre of rotation

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104
Q

What is centrifugal force?

A

A fictitious force from being opposite to centripetal force

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105
Q

In relation to pendulums what is angular amplitude?

A

Angular displacement from rest to maximum swing position

106
Q

In relation to pendulums what is a oscillation?

A

One complete swing to and from maximum position

107
Q

What is meant by the ‘length of pendulum’?

A

Distance from the pivot to the centre of gravity of the bob

108
Q

In relation to pendulums what is periodic time?

A

Time taken to complete one oscillation

109
Q

In relation to pendulums what is one cycle?

A

The motion completed in one period

110
Q

In relation to pendulums what is frequency?

A

Number of cycles completed in a unit of time

111
Q

In a pendulum does the mass of the bob have an effect on the periodic time?

A

No

112
Q

Periodic time of a pendulum increase when?

A

Pendulum length increases or gravity decreases

113
Q

What is damping?

A

Is a decrease of vibrations as a result of removing energy through resistance to motion

114
Q

What is vibration?

A

Mechanical oscillations about an equilibrium

115
Q

How is sound and pressure waves generated?

A

By vibrating structures

116
Q

What is free vibration?

A

When a mechanical input has an initial input and then its allowed to vibrate freely until it dampens out

117
Q

What is forced vibration?

A

When continuous force or motion is applied to a mechanical system

118
Q

What is a periodic vibration?

A

A vibration that repeats itself at standard intervals i.e harmonics

119
Q

On a harmonic graph what does the bottom number indicate?

A

The amount of waves there are in one time interval

120
Q

What is resonance?

A

The tendency of a system to oscillate at maximum amplitude at a certain frequency

121
Q

If a vibration isn’t in resonance what will happen?

A

It will never get big as it will act as a natural dampener

122
Q

What is velocity ratio?

A

How far he effort has to move in relation to the load

123
Q

What are the units for velocity ratio?

A

There isn’t any units as its a ratio

124
Q

What is mechanical advantage?

A

The ratio of force produced by a machine to the force applied to it

125
Q

What are the units for mechanical advantage?

A

There isn’t any units as its a ratio

126
Q

What are the three types of lever?

A

-first class lever
-second class lever
-third class lever

127
Q

In a first class lever where is the fulcrum positioned?

A

Between the effort and the resistance (normally In the middle)

128
Q

What are some examples of a first class lever?

A

Seesaw, crowbar, pliers

129
Q

What is the equation for mechanical advantage?

A

Resistance over effort

130
Q

What is the equation for mechanical advantage of a lever?

A

Effort x length of effort arm = resistance x length of resistance arm

131
Q

What is a second class lever?

A

When the fulcrum is at one end of the lever and the effort is applied to the opposite end i.e wheelbarrow

132
Q

What is a third class lever?

A

When the fulcrum is at one end and the resistance is at the opposite end with the effort somewhere between them i.e landing gear

133
Q

In relation to mechanical advantage, What is an incline plane?

A

A plane surface inclined to a horizontal plane at any angle but a right angle i.e luggage conveyor

134
Q

What is a pulley?

A

A wheel or set of wheels which a rapper or chain is pulled in order to lift or lower objects

135
Q

Is there any mechanical advantage in a single stationary pulley?

A

No

136
Q

If a single pulley is not fixed and the effort and weight move in the same direction, do you gain mechanical advantage?

A

Yes

137
Q

How do you gain mechanical advantage by using gears?

A

By varying the teeth ratio on the gears

138
Q

If both the drive gear and driven gear have the same number of teeth do you have mechanical advantage?

A

No its the same

139
Q

If the drive gear and the driven gear have different number of teeth do you have mechanical advantage?

A

Yes it can be more than or less than 1

140
Q

What is the equation for mechanical advantage of gears?

A

Driven over drive

141
Q

If you had a drive gear of 20 teeth and a driven gear of 40 teeth, what would the mechanical advantage be?

A

2

142
Q

What is torque proportional to?

A

Horsepower

143
Q

What is a spur gear?

A

When their teeth are cut straight across their circumference (look like spurs) i.e normal gears

144
Q

If you had two spur gears with external teeth connected together which way would the driven gear turn?

A

The opposite to the drive gear

145
Q

If you wanted two spur gears to turn in the same direction what would you need?

A

One gear to have an internal thread

146
Q

What is a bevel gear?

A

When the teeth are cut into a conical surface

147
Q

When would you use a bevel gear?

A

To transmit power between two shafts at an angle to each other

148
Q

What angle can bevel gears work up to?

A

Any less than 180˚ but typically used at 90˚

149
Q

The teeth on a bevel gear are external, what direction will the driven gear turn?

A

The opposite

150
Q

What is a worm gear?

A

A toothed wheel turning a revolving cylinder with a screw thread

151
Q

In a worm gear what is the driving component?

A

The cylinder (the worm)

152
Q

When is a worm gear used?

A

A large reduction in speed or high torque multiplication

153
Q

What are the difference peices in a sun and planet gear?

A

-sun gear
-planet gear
-ring gear
-a cage

154
Q

In the sun and planet gear what gear is the input?

A

The sun gear

155
Q

What is the output in a sun and planet gear?

A

The cage

156
Q

Why are sun and planet gears used?

A

When there is limited space and a need for a large reduction in speed and torque

157
Q

What is efficiency?

A

The ratio of work which is transferred to a useful form compared to the total input work

158
Q

What is efficiency measured in?

A

Percentage

159
Q

Why cant machines be 100% efficient?

A

Due to the losses like heat, friction, deflection, as well as wear and tear

160
Q

What is Isaac Newton’s first law of motion?

A

Every object remains in its state of rest or in uniform motion in a straight line, unless it is made to change by external forces impressing on it

161
Q

What is Isaac Newton’s second law of motion?

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

162
Q

What is Isaac Newton’s third law of motion?

A

Every action has an equal and opposite reaction

163
Q

What is the equation for force?

A

Force = mass x acceleration

164
Q

What is Newton’s third law of motion sometimes referred to?

A

The law of action and reaction

165
Q

What is the definition of mass?

A

The amount of matter in a body regardless of its volume or position

166
Q

What is an atomic mass unit?

A

The mass of a proton or neutron

167
Q

What is the equation for mass?

A

Mass = weight / gravitational acceleration

168
Q

What is the unit for mass?

A

Kilograms

169
Q

What is the definition of weight?

A

The gravitational force of attraction between the mass of the earth and the mass of a body

170
Q

What is the unit of weight?

A

Newtons or pounds

171
Q

Will the weight of a body increase, decrease or stay the same as it moves away from the earths centre?

A

It will decrease as gravity is getting lower

172
Q

What is the equation for weight?

A

Weight = mass x gravity

173
Q

What is inertia?

A

The property of matter that causes it to resist any change to is motion

174
Q

What does the amount of inertia depend on?

A

The amount of mass

175
Q

What is the definition of work?

A

The force causing a movement or a displacement of an object

176
Q

What is the equation for work?

A

Work = force x distance moved

177
Q

In the scientific sense if someone was holding a pile f books is work being done?

A

No because there is no movement

178
Q

What is work measured in?

A

Joules

179
Q

One joule is equal to?

A

One Newton meter

180
Q

What is the definition of power?

A

A measurement of the rate which work is done or at which energy is converted from one form to another

181
Q

What is the equation for power?

A

Power = work / time

182
Q

What is the unit for power?

A

Watt

183
Q

One watt is equal to?

A

One joule per second

184
Q

What is energy?

A

The capacity to do work?

185
Q

What is mechanical energy?

A

The energy held by a body after work has been done

186
Q

What are the different types of energy?

A

-potential energy
-kinetic energy
-total energy
-chemical energy
-heat

187
Q

What is potential energy?

A

When a body has energy due to its position or condition

188
Q

What is the equation for gravitational potential energy?

A

Mass x gravity x height

189
Q

What is kinetic energy?

A

Energy a body has due to its motion

190
Q

What is the equation for kinetic energy?

A

½ x mass x velocity^2

191
Q

What is total energy?

A

The sum of all different forms of energy in a system

192
Q

Can energy be created or destroyed?

A

No but it can be converted

193
Q

What is chemical energy?

A

The energy which is stored in the chemical bonds between atoms

194
Q

Chemical energy is a form of what other energy?

A

Potential energy

195
Q

What is heat energy?

A

The energy which a body possesses due to the kinetic energy and the potential energy of its molecules

196
Q

Thermal energy is also called?

A

Internal energy

197
Q

When converting energy from one form to another what is the common by product?

A

Heat

198
Q

What is the equation for efficiency?

A

(Useful energy / total energy) x 100

199
Q

What is momentum?

A

A vector quantity that describes mass in motion

200
Q

The more momentum something has the harder it is to?

A

Stop

201
Q

An objects momentum depends on what two variables?

A

Mass and velocity?

202
Q

The direction of the momentum vector is the same as?

A

The velocity

203
Q

What is the equation of momentum?

A

Mass x velocity

204
Q

What is the definition of a collision?

A

When two objects interact with one another, leading to transfer of kinetic energy and momentum

205
Q

What are the two types of collisions?

A

Elastic Collisions and in elastic collisions

206
Q

What are elastic collisions?

A

When two objects collide and bounce of each other to travel in opposite directions i.e newtons cradle

207
Q

What is an inelastic collision?

A

When two objects collide and merge together to travel in the same direction i.e a car crash

208
Q

What are the 3 key facts to an elastic collision?

A

-No loss of kinetic energy or momentum
-no heat exchange
-no damage

209
Q

What are the 4 key factors to elastic collisions?

A

-no loss of momentum
-kinetic energy lost
-heat created
-damage to objects

210
Q

What is the conservation of momentum equation?

A

M1u1+M2u2 = M1v1+M2v2

211
Q

What is a gyroscope / gyro?

A

An instrument that contains a disc that rotates about an axis at a high speed

212
Q

In a gyroscope what is the disc sometimes called?

A

A rotor

213
Q

What are the two important properties of a gyroscope?

A

Rigidity and precession

214
Q

What are the 4 factors that affect a gyroscope?

A

-rotor mass
-radius at which the mass acts
-speed of rotation
-bearing friction

215
Q

If you were to apply external force to change the direction of the rotor spin axis of a gyroscope what would happen?

A

The gyro resists the change and moves the force at right angles to the direction originally applied

216
Q

Why are gyros used to maintain orientation of an aircraft in flight?

A

Because once spinning they aren’t affected by the aircraft manoeuvres

217
Q

What is friction?

A

The force resisting the relative motion of materials rubbing against each other

218
Q

In relation to friction, When on horizontal surfaces what does the normal force become equal to?

A

The objects weight

219
Q

What is starting friction?

A

The friction as soon as the object starts to move

220
Q

What is starting friction sometimes refereed to as?

A

Break away force

221
Q

Does an object slide easier, harder, or same after the starting friction?

A

Easier due to momentum

222
Q

What is sliding friction?

A

The friction of two objects after the initial starting friction

223
Q

What does the amount of sliding friction depend on?

A

The nature of the material surfaces

224
Q

What is rolling friction?

A

Friction between a rolling body and the surface on which it rolls

225
Q

Which direction does friction go compared to the force applied to the object?

A

The opposite

226
Q

What are the effects between surfaces that are under friction?

A

Damage and an increase in heat

227
Q

Why is sliding fiction less than starting friction?

A

Because the force needed to start a body sliding is greater than the force to keep a body sliding

228
Q

Why is weight measured in newtons?

A

Because its a force

229
Q

What is impulse force?

A

A force applied over time

230
Q

What is the equation for density?

A

Density = mass / volume

231
Q

Although the standard unit for mass is kilograms (kg) and for volume is cubic metres (m^3), what is the norm units for a laboratory situation?

A

mass in grams (g) and volume in cubic centimetres (cm^3)

232
Q

If you wanted to convert from kg/m^3 to g/cm^3 what would you do?

A

Divide by 1,000

233
Q

If you wanted to convert from g/cm^3 to kg/m^3 what would you do?

A

Multiply by 1,000

234
Q

What is specific gravity (SG) sometimes referred to as?

A

Relative density

235
Q

What is used to compare the densities of two substances?

A

Specific gravity

236
Q

Densities of all liquids and solids are compared by using water at what temperature?

A

4˚C

237
Q

Densities of gases are compared by using air at what temperature?

A

Room temperature (20˚C or 68˚F)

238
Q

What is a hydrometer used for?

A

To determine the specific gravity of an electrolyte (battery liquid)

239
Q

What is viscosity?

A

The resistance of a fluid to a change in shape or relative movement

240
Q

What causes a fluid to have a high viscosity?

A

By internal friction between molecules

241
Q

If the temperature increases what happens to the viscosity of a liquid?

A

It decreases (becomes more runny)

242
Q

When temperature increases what happens to the viscosity of a gas?

A

It increases (more thick)

243
Q

What is fluid resistance / fluid friction?

A

When a solid object travels through a liquid or gas or indeed when a liquid or a gas travels through a solid

244
Q

What are the determining factors for fluid resistance/ fluid friction?

A

-viscosity of fluid
-shape surface texture
-shape of the object

245
Q

What is streamlining?

A

Decreasing the amount of restrictive force of fluid friction

246
Q

In relation to to streamlining why are composites used?

A

Reduces the need for riveting which makes it more efficient

247
Q

Under standard ISA conditions what is the speed of sound at sea level? (International standard atmosphere)

A

340m/s

248
Q

When airflow is faster than the speed of sound what is created?

A

A shock wave

249
Q

An increase in liquid pressure will have what affect on the liquid?

A

Increase the liquid internal temperature and reduce its viscosity

250
Q

What is the equation for pressure?

A

Pressure= force / area

251
Q

If you had three different sized water containers 10m^2, 100m^2, 150m^2, would the water pressure be the same at 3m?

A

Yes because water pressure only increases with depth

252
Q

If pressure is force over area, what is the equation for force?

A

Area x pressure

253
Q

If you had a piston with 1000 psi applied to both ends what would happen?

A

The piston would move to the rod end due to having a smaller surface area due to the rod taking up space

254
Q

What is static pressure?

A

The sum of gravity, applied force, and atmospheric pressure

255
Q

What is dynamic pressure?

A

The pressure that emerges from velocity of the fluid in motion

256
Q

What is total pressure?

A

The sum of static and dynamic pressure

257
Q

When flow velocity of a liquid increase what happens to the pressure?

A

Static pressure decreases and dynamic pressure increases

258
Q

What is pressure energy?

A

Energy stored in a fluid due to the force per area applied to it

259
Q

What is the equation for pressure energy?

A

Mass x pressure /density of fluid

260
Q

What is the equation of lift?

A

Lift = difference in pressure x area of wing

261
Q

According to pascals law what angle does pressure act at to the container?

A

90°

262
Q

Pascals law states that pressure is ——— throughout the enclosed liquid

A

Equal

B1 2-physics (3 decks)

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