Engineering Studies 2017 HSC exam pack

Students should:

• address the key words in the question, such as ‘explain’, ‘describe’, ‘compare’, ‘outline’
• consider using a graphical solution in mechanics questions
• be comfortable in the manipulation of SI units and prefixes to arrive at the required units for the question
• be familiar with correct terminology when describing/explaining engineering practices and concepts
• be aware of the ways common engineering materials may be formed into final products
• engage with the stimulus material in the question and relate their response to this context
• provide more than one example when the question states ‘using examples’.

Students should expect:

• engineering principles and concepts to be examined in new contexts and scenarios
• that there is more than one way to solve a mechanics problem. Students should be familiar with graphical solutions to minimise the time taken to solve a problem
• that questions are of varying difficulty
• to show their working as they may be able to access marks when their final answer is not correct
• to be able to transfer knowledge to similar areas, for example, applying knowledge about the solidification of metals to welding
• to support their answer with relevant comparisons and examples.

Students can prepare for this examination by:

• completing past HSC papers to familiarise themselves with the various types of questions
• practising engineering mechanics problems multiple times to ensure they understand
  how to provide a solution, rather than providing a solution that is simply memorised
• preparing study notes covering all aspects of the course content
• completing wide reading from a range of engineering studies resources.

In better responses, students were able to:

• use the correct and relevant engineering terminology
• clearly set out in order the processes/attributes and solution in a logical, succinct manner
• use labelled diagrams to enhance the complexity of their response
• use sound and clear mathematical methods to calculate correct answers
• answer the question within the space provided.

Question 21(a)

In better responses, students were able to:

• demonstrate their knowledge by appropriate use of examples
• use more than one example in which they elaborated on relevant information and properties
• use correct terminology to explain relevant properties or reasons for the varied use of gears in vehicles
• address a variety of reasons, not only the properties of gears.

Question 21(b)(i)

In better responses, students were able to:

• demonstrate knowledge of the unique properties of each of the manufacturing processes
• clearly compare the properties of each of these processes and show how they are similar and/or different.

Question 21(b)(ii)

In better responses, students were able to:

• show knowledge of the link between the process and the structural changes within the material
• demonstrate how this change affected the properties of the gear.

Question 21(c)

In better responses, students were able to:

• correctly use efficiency to calculate the velocity ratio and then multiply this by the driver gear
• identify that the intermediate gear could be used to help solve the problem, but that this was not the most efficient method.

Question 22(a)

In better responses, students were able to:

• outline the advantages of carbon fibre over steel frames
• use engineering terms such as ‘strength to weight ratio’ and ‘cyclic loading’. 

Question 22(b)

In better responses, students were able to:

• recognise the need for parts to be made separately then joined together, and that only half a frame would be made within the mould
• understand that the frame needed to be made of tubular sections then joined together, or correctly explain the process with reference to inflation of a ‘balloon’ inside the frame.

Question 22(c)

In better responses, students were able to:

• understand the units required and rearrange formulae to correctly calculate the answer
• clearly set out relevant formulae and show working in an organised manner leading to a correct solution.

Question 22(d)

In better responses, students were able to:

• correctly convert units for use in the formula to arrive at the final result in MPa
• realise the need to subtract the smaller area from the larger area to gain a correct cross-sectional area of the tube
• clearly set out all formulae and show clear working in an organised manner leading to a correct solution.

Question 23(a)

In better responses, students were able to:

• interpret the logic gate set-up and correctly determine the output.

Question 23(b)

In better responses, students were able to:

• demonstrate high levels of understanding of both common and zener diodes
• recognise the important role of breakdown voltage in differentiating a zener diode from a common diode.

Question 23(c)

In better responses, students were able to:

• correctly assemble the drawing from details in the exploded pictorial drawing
• apply correct AS 1100 standards to represent nuts and thread forms
• use the scale requested and place the assembled orthogonal drawing on the centre lines provided
• recognise that only the bracket is half-sectioned, because according to AS 1100 standards U-bolts and nuts are not sectioned.

Question 24(a)(i)

In better responses, students were able to:

• list relevant properties and then explain how each property made polypropylene suitable for its use in the context of the sled
• identify correct properties that are relevant for an engineer in selecting a material for this application
• identify a number of relevant properties.

Question 24(a)(ii)

In better responses students were able to:

• name and then correctly describe the process in correct order
• display conceptual knowledge of the forming method used for polypropylene.

Question 24(b)(i)

In better responses students were able to:

• correctly label each force on the free-body diagram
• show all four forces with correct line of action and sense
• set out a free-body diagram that was clear and with forces easily identified.

Question 24(b)(ii)

Angle of static friction method (analytical)

In better responses students were able to:

• correctly use tan−1 𝜇 or 𝜇 = tan 𝜃 to find the angle of static friction
• construct a force polygon that used the angle of static friction as the angle between the weight (mg) and the resultant of the normal and the frictional force
• correctly determine the internal angles of the force polygon of weight (mg), resultant and pulling force
• use a suitable mathematical solution to determine the magnitude of the pulling force.

OR

Angle of static friction method (graphical)

In better responses students were able to:

• correctly use tan−1 𝜇 or 𝜇 = tan 𝜃 to find the angle of static friction
• use a scaled drawing of the force polygon using line of action and sense from their free-body diagram
• measure the length of the pulling force on a scaled drawing
• apply the scale to determine the magnitude of the pulling force.

OR

Summing forces method

In better responses students were able to:

• sum the forces horizontally and identify that the magnitude of the frictional force in one direction is equal to the horizontal component of the pulling force in the opposite direction at the point of movement
• sum the forces vertically and identify that the weight force of the sled is reduced by the vertical component of the pulling force, then realise that as a result of this reduction the frictional force is also reduced
• use a suitable mathematical method to determine the magnitude of the pulling force.

Question 25(a)(i)

In better responses, students were able to:

• follow a logical sequence of steps down the page using suitable labels and formulae to provide a clear solution
• demonstrate the vector addition of the components of the reaction at A. This ensured they had the correct direction and sense for this reaction
• recognise that the horizontal truss with reactions on a vertical surface is solved in exactly the same way as more typical truss situations with the truss on a horizontal surface.

Question 25(a)(ii)

In better responses, students were able to:

• recognise that method of sections was the best method to determine the force and nature of member C
• place a section plane in the correct position and then use moments to correctly determine the force and nature in member C
• realise this problem could not be solved by summing vertical forces as member C is horizontal.

Question 25(a)(iii)

In better responses, students were able to:

• demonstrate their understanding that concrete is good in compression and can be cast in situ to take the shape of the hole and make a secure footing.

Question 25(b)(i)

In better responses, students were able to:

• visualise what this truck chassis would look like and what part of the RHS was the flange
• demonstrate their understanding that welding would involve melting the chassis and thus some form of recrystallisation would take place. They were then able to explain that this change to the structure could cause cracking
• explain that drilling the flanges would affect the cross-sectional area or create stress raisers which could then lead to cracking.

Question 25(b)(ii)

In better responses, students were able to:

• draw weld penetration of both surfaces, showing the original elongated grain structure of the plate and chassis rail with some evidence of recrystallised (equiaxed) grains around the weld
• recognise the weld involved solidification of molten metal, and understand that this would create solidification features such as chill crystals, columnar grains and equiaxed grains
• use labels to enhance the information conveyed in their drawing.

Question 26(a)

In better responses, students were able to:

• interpret the concept of Pascal’s Principle
• identify the correct formula to calculate area
• select a suitable formula and method to solve for the force required
• use compatible SI units for pressure.

Question 26(b)(i)

In better responses, students were able to:

• identify the required development shape
• identify and use construction to generate true lengths
• construct a half-development using identified and generated true lengths.

Question 26(b)(ii)

In better responses, students were able to:

• calculate the correct shear area when punching a hole
• select a suitable formula and method to solve for the force required
• use compatible SI units for stress.

Question 26(c)

In better responses, students were able to:

• identify the changes in the structure of an aluminium alloy due to precipitation (age) hardening
• explain how precipitation hardening changes the structure and the properties of aluminium alloys.

Question 27(a)

In better responses, students were able to:

• recognise the importance of routine testing and indicate, using an example, the effect the testing has on components
• identify the cause within service that creates the need for routine testing, using practical examples from fields such as aeronautics and transportation.

Question 27(b)

In better responses, students were able to:

• draw on their knowledge of testing to explain how each criterion would be assessed. Responses commonly included: computer simulations; prototyping; non-destructive tests; tensile and compression testing
• give good explanations of the use of wind tunnels
• recommend testing materials in a salty environment similar to the coastal container wharf
• explain how each engineering design element would be tested and assessed, breaking the response up into sections that reflected the elements. Some students used a broader approach to explain the testing of the elements to assess the criteria
• develop a method of clearly addressing each element of the question, providing cause and effect discussions which proved quite effective in this question.