1
Q
Why does a millwright need to understand trade science?
A
The millwright trade is based on applied scientific principles
2
Q
Define atoms
A
Atoms - are single units of special substances called elements.
3
Q
Define molecules
A
Molecules - when atoms of elements unite to form more complex structures (called molecules)
4
Q
Define elements
A
Elements - are materials containing only one type of atom
5
Q
Define compounds
A
Compound- is the product of two or more atoms that unite chemically
6
Q
Define a mixture
A
Mixture - when two or more elements or compounds may combine so that molecules in the resulting material retain their orignal properties
7
Q
Is brass a mixture or a compound?
A
Brass is an alloy which is a mixture of a metal with other mental or non metals.
Brass is an alloy of copper and zinc therefore it’s a mixture.
8
Q
Define alloys
A
Alloys- mixture of a metal with other metals or non metals
9
Q
What is brass an alloy of?
A
Copper and zinc
10
Q
What are the physical states of matter? (3)
A
Solid
Liquid
Gas
11
Q
Can all forms of matter be changed from one physical state to another and then be returned to its original state?
A
No
Many substances cannot change from one physical state to another without becoming permanently unrecognizable.
ex- a block of oak can’t be changed into a liquid then back to a block of oak. But water can be changed to ice and back
12
Q
Define cohesive forces
A
Cohesive forces - molecules in solids are strongly attracted to one another and this attraction is called cohesive forces.
It limits the space around individual molecules, packing closely so that solids hold definite shapes
Ex. Steel rod is held together by high cohesive forces. Where gases have little cohesive forces
13
Q
Define adhesive forces
A
Adhesive forces- molecules that are not alike often share a force of attraction similar to cohesion. This intermolecular force is referred to as adhesive forces.
Ex. Water wetting cement
14
Q
Can adhesive forces be stronger than cohesive forces?
A
Yes.
Ex. Certain epoxies
15
Q
Define mass
A
Mass is a measurement of the quantity of material in a body
16
Q
What determines the weight of an object
A
Gravity in relation to mass
17
Q
Define weight
A
The force of gravity acting on a mass
18
Q
What are the metric units for force? (1)
A
Newtons (N)
19
Q
Weights are often expressed (incorrectly) in what metric measurements?
A
Grams (g)
Kilograms (kg)
20
Q
What is the imperial units to measure force?
A
Pounds force (lbf)
21
Q
What is the imperial unit to express weight?
A
Pounds (lbs)
22
Q
Define volume
A
Volume is a measurement of the amount of space an object occupies
23
Q
How do you find the volume of an object such as a rectangular box?
A
Volume = length x width x height
V=LxWxH
24
Q
How would you find the volume of a cylinder object?
A
Volume = area of an end x height
V=3.14 x R squared x height
25
What unit is volume typically shown as in the metric system? (2)
Cubic meters (m3)
Litres (L)
26
What is the litre equal to in cubic decimetres?
1L =1 dm3
27
What is 1 Litre equal to in cubic centimetres?
1L =1000 cm3
28
Volume is typically shown in what imperial units? (3)
Cubic inches (in3)
Cubic feet (ft3)
Us gallons (G)
29
What is 1 us gallon equal to in cubic inches?
1 us gal =3.785 liters 231in3
30
What is 1 imperial gallon typically equal to in cubic inches?
1 imperial gallon =4.546 liters 277in3
31
Define density
Density - indicates the mass of a body in a given volume. The more molecules packed into a given volume of a substance the more dense it is.
32
What is the equation to find density given the mass and volume?
Density = mass / volume
33
Define relative density
Relative density - compared the density of materials to other substances
34
What are the reference materials for specific gravity of solids and liquids?
Water
35
What are the reference materials for specific gravity of gases?
Air
36
Define a solid
Solids - maintain their own shape without a container
37
Define mechanical properties
The characteristics of a solid that are displayed when a force is applied to it
38
Define strength
Strength - the ability to withstand gradually applied forces without rupturing
39
Define ultimate strength
Ultimate strength - the point at which the material ruptures
40
Define stress
Stress - the force per unit area acting on an object to change it’s dimensions
41
What is the metric unit used to show stress
Pascal (Pa)
42
What is 1 pascal equal to in Newton metres squared?
1Pa=1N/m2
43
How would you find stress if you had the force and area?
Stress = force / area
44
Define strain
Strain - the ratio of the extension per unit length when a force is applied
45
What unit is used to express strain?
No unit as it’s a ratio
46
How would you find strain if given the extension and original length?
Strain = extension / original length
47
Define tensile strength
Tensile strength - the ability of a material to resist being pulled apart by external forces
48
Define ultimate tensile strength
Ultimate tensile strength - the maximum amount of stress the material can withstand before breaking
49
Define compressive strength
Compressive strength- the ability to resist external forces that push into it against the material
50
Define ultimate compressive strength
The maximum compressive stress that a material can withstand before its surface area changes
51
Define shear strength
Shear strength - the ability to resist forces that try to slide part of the object along itself
52
Define ultimate shear strength
Ultimate shear strength - the maximum stress the material can withstand before it’s cut apart
53
Define fatigue strength
Fatigue strength - the ability to withstand repeatedly alternating stresses
54
Define elasticity
Elasticity - the ability of a material to return to its original dimensions after it has been acted on by a force
55
Define elastic limit (yield strength)
Elastic limit (yield strength) - maximum force that a solid can withstand without it permanently being deformed
56
Define plasticity
Plasticity- the ability for material to retain a shape permanently after a deforming force is removed
57
Define ductility
Ductility - a materials ability to stretch and maintain the new shape
58
Define malleability
Malleability - the ability of a material to be permanently deformed by compression forces
59
Define brittleness
Brittleness - material that breaks without noticeable plastic deformation. It is also known as the absence of malleability
60
Define toughness
Toughness - the ability of a material to withstand shock loads
61
Define hardness
Hardness - a materials ability to resist a force that is trying to penetrate it.
62
What are the physical properties of solids?
Physical properties of solids are characteristics of their interactions with various forms of energy.
63
What are the 3 physical properties to be aware of in industry?
Electrical
Thermal conductivity
Thermal expansion
64
What are the chemical properties of solids that millwright deal with? (3)
Composition
Corrosion resistance
Electrochemical properties
Chemical properties of solids are characteristics that relate to the interactions of the particular elements and compounds in the material and the environment.
65
What effects does electrolysis have on metal?
Corrosion
When two different metals are in contact with each other and water is present, an electric current is produced
This has a chemical effect that corrodes the metals or disintegrates them.
66
What is the galvanic series in regards to metals?
A list of metals that corrode each other
67
Describe the properties of liquids
Liquids - nearly incompressible, no definitive shape, but take the shape of their container
68
Describe volatility
Volatility- a measure of how quickly a liquid vaporizes
A liquid is said to be highly volatile if it changes from a liquid to a gas quickly
69
Define viscosity
Viscosity - the measure of a liquids resistance to flow
The higher the viscosity the more resistance the liquid has to be poured
70
Describe the properties of gases
Gases - widely spaced and can act independently, moving freely. They can be expanded or compressed into any space regardless of size
71
How is the pressure of gases measured?
Gases are measured by using a gauge
72
What is atmospheric pressure? (Numeral )
14.7psi
73
Describe internal energy
Internal energy (thermal energy) - the molecular movement of the materials molecules
A materials molecules are in constant, random motion. This molecular movement is an energy form called thermal or internal energy
74
Is a materials temperature directly related to its internal energy?
No
Temperature is simply a measurement of the relative hotness or coldness of a body it is not directly related to internal energy
75
Define heat
The energy that is transferred from a hot object to a cooler one
Heat is energy in transit from a body at a higher temperature to a body at a lower temperature
76
Name the instruments used to measure temperature (4)
- Liquid expansion thermometers
- Bi-metallic strip thermometers
- Pyrometers
- Thermocouples
Liquid expansion thermometers - consist of a small reservoir and fine tube. The reservoir is typically filled with coloured alcohol or mercury
Bi-metallic strip thermometers- two strips of different metals bonded together. Can be bent or coiled and linked to a pointer. As the metals expand in heat it moves the pointer
Pyrometers - measures temperatures beyond typical range
Thermocouples - used to measure high temperature they consist of an electrical circuit terminating with the junction of two metals
77
What are the units used to measure heat (energy in transit)
Joules (j)
Kilojoules (kj)
Megajoules (mj)
British thermal units (btu)
78
Define a British thermal unit
British thermal unit - amount of heat needed to change the temperature of 1lb of water by 1 degree Fahrenheit 
79
How many British thermal units in a kilojoule?
1kj =0.948 BTUs
80
Define thermal expansion
Thermal expansion - refers to the expansion of matter when heated
81
Define linear expansion
Linear expansion - refers to a change in dimensions of an object in a particular direction (ie: length, width, height or diameter)
82
Define coefficient of linear expansion
Coefficient of linear expansion- the different rates of linear expansion of various materials
83
Define volume expansion
Volume expansion - similar to thermal expansion but the substance expands in all directions.
84
Define coefficient of volume expansion
The coefficient for volume expansion is 3x the coefficient of linear expansion
85
Describe how heat is transferred from one object to another (3)
Conduction
Convection
Radiation
86
Define thermal conductivity
Conduction - heat travels directly through a material
87
Define force
Force- an external agent that causes a change in motion or stress in a body
88
Describe Newton’s first law of motion
An object tends to keep at rest or motion unless it is acted in by some external force
A body at rest and a body in motion will remain in motion at the same speed and in the same direction unless acted on by some unbalanced force
89
Describe Newton’s second law of motion
Gives a way to calculate force
F=m x a
Force = mass x acceleration
The size of a force (f) on an object is equal to the product of mass (m) and acceleration (a) of the object
90
Describe Newton’s third law of motion
For every action there is an equal and opposite reaction
91
What is the equation to find force using Newton’s second law
F = m x a
Force = mass x acceleration
92
Define velocity
Velocity - the distance a body moves in one direction per unit time
93
What’s the equation to find velocity
V = d/t
Velocity = distance / time
94
Define speed
Speed - the distance a body moves over time but does not take direction into account
95
Define acceleration
Acceleration - velocity or speed changes in the positive direction
A = (Vf - Va) / t
Acceleration = (final velocity - orignal velocity) / time
96
How are rotational motion and periphery speed expressed
The speed of a rotating object is measured by the number of revolutions it makes every minute:
Revolutions per minute (Rpm)
97
What are the 3 classifications of energy
Potential (static)
Kinetic (dynamic)
Radiant (electromagnetic)
98
Define potential energy
Potential (static) energy - when an object is in position to do work but no work is being done
It has the potential to do work
99
Define kinetic energy
Kinetic energy - occurs when an object moves
100
Define the law of conservation of energy
Energy cannot be created or destroyed but it may be converted from one form to another
101
Define work
Work - is done whenever one kind of energy is converted into another type of energy
102
How do you find work using an equation
W = f x d
Work = force x distance
103
Define power
Power is the rate at which work is done
104
How do you find power in an equation
P = w/t
Power = work / time
105
How is power expressed?
Units of work per unit time
106
Define mechanical advantage
Mechanical advantage- is the ratio of the work done to the effort required
107
Define efficiency in terms of mechanical advantage
Efficiency- when work is done with very little loss of energy to other processes such as friction.
108
Define class 1 levers
Have a fulcrum between the resistant force and the effort
Ex:
Scissors
Crowbars
Bolt cutters
Pliers
109
Define class 2 levers
The resistance is between the fulcrum and the effort
Ex:
Wheelbarrow
Nut cracker
110
Define a class 3 lever
The effort is applied between the resistance and the fulcrum
Ex:
Tweezers
Cranes
Back hoe
111
What class of lever is scissors?
Class 1
112
What class of lever is a wheelbarrow?
Class 2
113
What class lever is ratchet
Class 2
114
How do you tell which class of lever a wheel and axle system falls into?
If the axle or the wheel is used to apply the effort
When the wheel is used to apply the effort it is a class 2
When the axle is used to apply the effort it is a class 3
115
What class is a driven axle and wheel of a vehicle
Class 3
116
What is the purpose of a single fixed pulley and load line?
To change directions of the force
It does NOT change resistance or applied force
117
How do you quickly find the mechanical advantage (MA) in a multiple pulley system?
By counting the number of rope strands supporting the load
118
If there is 6 rope strands supporting a load what is the mechanical advantage (MA)
6
119
How is the mechanical advantage (MA) found in belt drives?
MA= driven diameter/ drive diameter
120
121
In chain and gear drives how is the mechanical advantage found?
MA = # teeth on driven / # of teeth on drive
122
Fill in the blank :
If the driven element is larger than the drive element the rpm of the driven shaft is ____________ than the rpm of the driver
Less
123
Fill in the blank :
If the driven element is smaller than the drive element the rpm of the driven shaft is ____________ than the rpm of the driver
Greater
124
If two shafts are connected by gears what directions do they rotate?
Opposite
125
If two shafts are connected by belt or chain what directions do they rotate
The same direction
126
What is the purpose of idlers when used within a drive unit
To either change the direction of rotation or aid in the support of long distances between drive and driven elements
127
Do idlers affect the ratios in a drive system
No
128
Define a compound drive unit
Has two or more drive elements and two or more driven elements
129
What simple machine is screws derived from
Incline plane
130
What is the benefit of an inclined plane?
Inclined plane - allows you to exert a small effort over a larger distance to move greater resisting forces
131
What do wedges, cams, and screws all have in common?
They are all derived from incline planes
132
What is the distance between two adjacent threads called on a screw?
The pitch
133
What has a higher mechanical advantage standard thread screws or fine?
Fine
134
If screws have such high mechanical advantage (MA) why are they considered inefficient machines?
The friction development between the threads
135
How is mechanical advantage achieved in hydraulics?
By using a small piston to move a bigger one while using a series of check valves to allow higher pressure into the larger piston
136
What are compound machines?
When two or more simple machines are coupled together
This allows for greater mechanical advantage
