Question 1
Identify an example of a recent innovation that has led to an improvement in the resource efficiency of a product that you are familiar with (any product, invention, mode of transport etc).
An improvement in resource efficiency might involve, for example, a reduction in the amount of material used to manufacture the product, a reduction in the energy consumption of the product in use, extending the product’s lifetime, or making it more recyclable or reusable at the end of its life.
Write an account of the product and the innovation you have chosen that includes the following:
•    an introduction to the product and its purpose
•    a description of the innovation
•    an explanation of how the innovation improves resource efficiency.
Your answer should be no more than 500 words long and must include at least one diagram or photograph of the chosen product
Write in academic English aimed at a reader who does not share your knowledge of the product or of any specific area of engineering that may be involved.
A further 5 marks will be awarded for an appropriate writing style, including correct punctuation, spelling and grammar.

Question 2
In Week 17 you observed and recorded measurements from a creep experiment. The material tested was a particular type of aluminium alloy used in aeroplane structures. Figure 1 shows standard creep samples before and after a similar creep test. The lower sample underwent severe necking, before breaking at the thinnest point
The drawing used to machine the sample from a rectangular block of material is shown in Figure 2. This shows that the ‘gauge length’ (the length of the central portion of the sample over which the load was applied) at the start of the experiment was 50.00 mm.
During the experiment a constant tensile load of 3.568 kN was applied to the sample. This caused the sample to extend.
In Question 2a you are asked to calculate the stress acting on parts of the sample at the beginning and end of the experiment.
All your answers to Question 2a should be given in SI units (with the unit stated) to 3 significant figures.
2a.
i.    To calculate the stress on the sample due to the applied tensile load you need to know the area over which this force is acting. Using information from Figure 2, show that the relevant cross-sectional area of the sample within the gauge length at the start of the experiment is 50.3 mm2 (to 3 s.f.).
ii.    Using the value for the cross-sectional area from Question 2a(i), calculate the stress experienced by the test specimen within its gauge length, at the start of the test.
iii.    The applied load remains constant throughout the test. At the end of the test, the diameter of the test specimen shown in Figure 1 at the location where necking occurred was measured and the cross-sectional area calculated to be 15.0 mm2. Based on the reduced cross-sectional area at the necking location, calculate the stress in the neck at the point of failure.
iv.    Compare the value of stress at the beginning of the test (your answer to Question 2a(ii)) with the stress value at the point of failure (your answer to Question 2a(iii)) and use these values to calculate the percentage increase in the value of stress due to ‘necking’ of the test specimen from the start of the test to the point of failure.

2c
The equation below is a polynomial of order 4, fitted to the data recorded in a creep test conducted on a particular type of steel, for an elapsed time between 10 to 20 hours.
The data were recorded for % strain versus elapsed time in hours.
Use this equation to calculate the creep strain rate at 15 hours elapsed time. Give your answer to 1 significant figure.

Question 3
Polyethylene terephthalate (PET) is a hydrocarbon polymer produced from the reaction of chemicals obtained from crude oil. PET is used in many applications including the manufacture of soft drink bottles. Like plastic bags, PET bottles present challenges to the engineering community when they reach the end of their lives.
PET bottles are often re-used; for example they can be refilled with tap water (although the bottle manufacturers’ discourage this on hygiene grounds), or cylinders cut from bottles can be used in the garden to protect seedlings and young plants.
This still leaves around 200,000 tonnes of waste PET bottle for treatment or disposal in the UK each year. Two possible disposal options are:
•    PET can be recycled into new bottles or other products.
•    PET releases a lot of energy when burned, so it is a useful potential fuel for waste fired power stations along with other components of the waste stream. (Apart from the greenhouse gas CO2, PET does not release harmful chemicals into the atmosphere when burned).

3a
Think about the activities involved in producing a product, and getting it to market. For this question, make a list to cover each process in the chain of activities needed to produce a PET bottle filled with still water, from the raw materials to the point of purchase by a consumer. The first three stages have been provided below. You are not expected to include details of the manufacturing method.
Continue to use bullet-points to complete the list of stages. Each stage should be 1-2 sentences. (Tip: 8 more processes should be listed)
o    extraction of crude oil from the ground
o    refining of the crude oil and production of chemicals needed to produce PET
o    production of PET and processing into pellets
o    ……

3b
The price of the raw PET granules used for bottle manufacture is £860 per tonne and the drink manufacturers pay 4 pence for each empty bottle, excluding the screw cap. Assuming that a bottle can be approximated to a cylinder that is open at one end, with height 230 mm, diameter 75 mm and constant material thickness 0.40 mm, estimate the value added from the transformation of a kilogram of granules into bottles.
The density of PET is 1380 kg m−3.
Explain each step in your working and give your answer to the nearest 10 pence.

3c
Suggest two difficulties in recycling PET bottles back to new bottles and suggest a way of overcoming one of these difficulties.

3d
The chemical formula for one repeat unit of the PET polymer is C10H8O4. Write down a balanced chemical equation for the complete combustion of one repeat unit of PET in oxygen to form carbon dioxide and water. Explain how you can test that your equation is balanced.
3e
The heat of combustion of PET is 30.2 MJ kg-1. If PET bottles are burned in a waste-fired power station that generates electricity with an overall efficiency of 25%, calculate how much useful electrical energy is generated when 1,000 tonnes of PET is burned. Give your answer in units of MJ to 3 significant figures and explain your working

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