Unit 4 (Final Production)

Question 1

Distinguish between mass and weight (2)

Answer 1

Mass- constant regardless of gravity, measured in kg

Weight- resultant force of gravity on mass, measured in newtons (N)

Question 2

Distinguish between hardness, stiffness and toughness (3)

Answer 2

Hardness- resistance to scratching or penetration

Stiffness- resistance to bending

Toughness- ability to deform without cracking, or resist fracturing on impact

Question 3

Distinguish between elasticity and plasticity (2)

Answer 3

Elasticity- ability of a material to be deformed, and then return to its original position

Plasticity- ability of a material to be formed into a new shape

Question 4

Describe Young’s modulus, and explain the difference between stress and strain

Answer 4

Young’s modulus- a graph depicting the changes in strain with applied stress

Stress- tensile force applied to an area

Strain- percentage of change in the length when the force is applied

Question 5

What is the quality that allows certain smart materials to change colour when exposed to light?

Answer 5

Photochromacity

Question 6

What is the quality that allows certain smart materials to release an electric charge when deformed?

Answer 6

Piezoelectricity

Question 7

What is the quality that allows certain smart materials to change their viscosity when a magnetic field is applied?

What about when an electrical force is applied?

Answer 7

Magneto-rheostatic

Electro-rheostatic

Question 8

What is the quality that allows certain smart materials to generate electricity when heat is applied?

Answer 8

Thermoelectricity

Question 9

How does the rate of cooling affect grain size in metals? What are the advantages of larger grains? (1 + 4)

Answer 9

Slower cooling –> larger grains –>

increased tensile strength
increased toughness
increased ductility
increased malleability

Question 10

Define work hardening and tempering (1 + 1)

Answer 10

Work hardening- the process of increasing the hardness of a metal by applying forces while the metal is cold

Tempering- the application of heat after work hardening (reduces hardness and stiffness, but increases toughness and ductility)

Question 10

Distinguish the qualities of a superalloy (2)

Answer 10

Superalloys are alloys that exhibit high mechanical strength, resistance to creep (expansion/ deformation) and resistance to oxidation (eg. rust)

Question 11

How can metals be categorised? (3)

Answer 11

Ferrous (eg. steel, iron)

Non-ferrous (eg. aluminum, copper)

Alloy (eg. brass, tin)

Question 12

Give the general qualities of softwoods, with examples (4 + 3)

Answer 12

low density (lower hardness)
high flexibility (lower mechanical strength)
generally lighter coloured
fast growing, considered renewable

eg. Douglas fir, sugar pine, redwood

Question 13

Give the general qualities of hardwoods, with examples (4 + 3)

Answer 13

higher density (higher hardness)
low flexibility (higher mechanical strength)
smooth, range of colours
slow growing, not considered renewable

eg. white oak, American sycamore, black cherry

Question 14

List examples of engineered woods and their advantages (3 + 3)

Answer 14

Plywood (strong in compression)
MDF (strong, smooth finish)
Fibreboard (cheap, lightweight)

Question 15

Distinguish between seasoning, treating and finishing timber (3)

Answer 15

Seasoning- removing moisture through long term drying processes

Treating- chemical applications to improve specific qualities, eg. protection from insects/ rot, weathering resistance, etc.

Finishing- improving the aesthetic qualities through the application of a finish, eg stains, oils, waxes

Question 16

List types of glass and their advantageous properties (4)

Answer 16

Borosilicate (high thermal resistance)
Tempered (high shock resistance)
Fibreglass (flexibility)
Laminated (anti-shatter)

Question 17

List the general qualities of glass (6)

Answer 17

colour variation
transparency
high compressive strength
low tensile strength
high hardness
Nonporous, non-toxic, unreactive

Question 18

Distinguish between thermoplastics and thermosets (2)

Answer 18

thermoplastics can be heated and reformed

thermosets cannot be reheated or reformed

Question 19

Give the general qualities of thermoplastics, with examples (4 + 3)

Answer 19

low production cost
easy to injection mold
low stiffness/ high flexibility
can be reshaped after heating

eg. polypropylene, polyethylene, high impact polystyrene

Question 20

Give the general qualities of thermosets, with examples (4 + 3)

Answer 20

higher production cost
heat resistant
high stiffness/ low flexibility
cannot be reshaped after heating

eg. urea-formaldehyde, polyurethane, melamine

Question 21

Distinguish between fibres, yarns, threads and fabric (4)

Answer 21

fibres- raw form
yarn- long continuous fibre
thread- thin yarn used in sewing
fabric- cloth produced by weaving, knitting, felting etc.

Question 22

Compare the properties of natural and synthetic fibres (4 +4)

Answer 22

NATURAL
high absorbency
low tensile strength
low elasticity
will burn at high temp.

SYNTHETIC
low absorbency
high tensile strength
high elasticity
will burn and melt at high temp.

Question 23

Give examples of natural fibres, and an advantage of each (3 + 3)

Answer 23

wool (insulative, even when wet)

cotton (most prevalent, low cost)

silk (highest strength of natural fibres)

Question 24

Give examples of synthetic fibres, and an advantage of each (3 + 3)

Answer 24

nylon (abrasion resistant)

polyester (high strength)

lycra (very high elasticity)