Chapter 1 Trade Science (Free Lecture 1)
Chapter 1 Trade Science
The mechanics millwright trade is based on applied scientific principles. These principles are constantly applied by millwrights, often without realizing it. Sometimes the millwright needs to think of a problem through using these principles, or to calculate a dimension, a load , or some of these important principles.
Atoms and Molecules
All matter is composed of atoms. Atoms are single units of special substances called elements.
118 elements currently on the periodic table in the Universe are hydrogen, oxygen, carbon, copper, lead, silver and gold. Etc.How Many Elements Can Be Found Naturally? (thoughtco.com)
The arrangement and structure of the molecules in a substance are unique.
Compounds and mixtures
Compounds( Chemical material)
A compound is the product of more than two atoms that unite chemically.
Mixtures( physics material)
Two or more elements or compounds may combine so that the molecules in the resulting material retain their original properties.
Alloys
Alloys are mixtures of a metal with other metals or non-metals.
Physical states of matter
Matter exists in three physical states i.e. gas, liquid and solid.
Molecular attractions in matter
The physical state of a substance is determined by the spacing and motion of the individual molecules.
Cohesive force
Cohesive force is called by molecules in solids that are strongly attracted to one another .
Liquids are also composed of tightly packed molecules but the cohesive force is not as great as that found in solids.
Gas molecules exhibit little cohesion.
Adhesive forces
Molecules that are not alike often share a force of attraction similar to cohesion.
Mass, weight, volume, and density
Matter has several physical properties, including mass, volume, and density that are different from mechanical properties .
Mass and weight
Mass is a measurement of the quantity of material in a body.
Weight is called by the force of gravity on earth.
In the metric system the unit of force is called a newton(N). In everyday life, weights are often expressed(incorrectly) in grams(g) or kilograms(kg) rather than newtons.
The imperial system uses the unit pounds-force(lbs) to express force, including weight.
In the US, the unit pounds(lb) is often used to express weight, although this is inaccurate.
Volume
volume is a measurement of the amount of space an object occupies.
volume= Length *Width*Height
Volume of cylindrical object such as an oil tank, you multiply the area of the end times the height.
Volume=Area of an end x Height
V=r2H
Note that (pronounced pi) stand for the number 3.14159…, often rounded off to 3.142.
In the imperial units include cubic inches (in3).cubic feet(ft3), and imperial and US gallons.
1 imperial gal=277 in3
1 US gal=231 in3
Density
Density=M/V
In the formula, M-Mass
V-in a given volume
Properties of solids: Solids maintain their own shape without a container.
Mechanical properties of solids: these are the characteristics of a solid that are displayed when a force is applied to it.
Ultimate strength: Strength is the ability to withstand gradually applied forces without rupturing. These forces tensile, compressive, or shear. discuss them later
–Stress and strain
Stress= force/area
Strain=extension/ original length
Tensile strength： Tensile strength is the ability of a material to resist being pulled apart by external force.
UTS– The Ultimate Tensile Strength
Physical properties of solids
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