Engineering Studies 2018 HSC exam pack

Students should:

• consider using a graphical solution in mechanics questions to minimise the time taken to solve a problem
• 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
• support their answer with relevant comparisons and examples
• provide more than one example/advantage when the question states ‘using examples/advantages’
• show their working as they may be able to access marks when their final answer is not correct
• use vector diagrams where appropriate to demonstrate their solutions to force analysis problems
• transfer their engineering knowledge, learned through the module topics, to other applications. Engineering Studies looks at how engineering is applied to engineering solutions, hence students are encouraged to be well read about engineering applications to ensure they can apply their knowledge to unexpected fields, for example, a fidget spinner.

Question 21(a)

In better responses, students were able to:

• describe the two systems and their function.

Areas for students to improve include:

• identifying that it is a ‘self-drive’ vehicle and the two systems inform the autonomous operation without the input of the ‘driver’
• outlining how the GPS and sensor systems operate providing features and characteristics of the two systems which enable their function
• detailing specifically how multiple inputs and outputs are used to inform an operating system in order to allow the whole system to function.

Question 21(b)

In better responses, students were able to:

• indicate in general terms the advantages of electric motors.

Areas for students to improve include:

• providing advantages of electric motors, for example, use of instantaneous torque instead of max torque at low rpm
• being specific in their responses, for example, being environmentally friendly or more efficient.

Question 21(c)

In better responses, students were able to:

• apply the correct formula
• use correct mathematical processes to derive the correct answer.

Areas for students to improve include correctly:

• substituting values into formula including conversion to SI units
• squaring the velocity and converting the answer to kilojoules (kJ) as the question required.

Question 21(d)

In better responses, students were able to:

• demonstrate a good understanding of the operation of the AND and OR gates
• succinctly describe the operation of logic gates
• work through each gate and possible outcomes from the possible inputs, and then move to the next gate and explain the relationship.

Areas for students to improve include:

• working methodically through the scenario of the gate arrangement
• comprehensively describing the possible inputs and outputs of each gate
• describing in detail how the gate interacted in the given scenario.

Question 22

In better responses, students were able to:

• articulate and explain mechanical properties relating to telecommunication technologies (a)
• explain the characteristics and functions relating to transmission devices found in telecommunication devices (a)
• provide a clear understanding of materials and their application in coaxial and optical fibres (b)
• describe in detail the functional characteristics of a diode and application in a telecommunication circuit (c)
• apply and calculate the resistance in an electrical circuit equation (d).

Areas for students to improve include:

• providing a clear and cohesive explanation of materials and their application in telecommunication networks (a)
• ensuring they link the function and application of a diode in their responses (c)
• applying the correct values and formula to an electrical circuit equation (d).

Question 23(a)

In better responses, students were able to:

• use appropriate terms to link the part and its in-service performance requirements
• demonstrate a knowledge of appropriate manufacturing processes for metals and polymers.

Areas for students to improve include:

• associating the term 'strength' with a particular type of strength
• identifying the parts in a device/structure, linking them with required engineering properties and appropriate manufacturing processes.

Question 23(b)(i)

In better responses, students were able to:

• identify values for load and extension below the yield point and combine these with given data for area and length to correctly calculate Young's Modulus
• convert units for force, area, length and stress correctly.

Areas for students to improve include:

• understanding key aspects of a load/extension diagram and how these can be used to calculate Young's Modulus
• calculations involving SI units, for example, kN, m² and GPa.

Question 23(b)(ii)

In better responses, students were able to:

• describe the difference between elastic and plastic deformation of a ductile material
• identify that elastic deformation occurs below the yield point of a material.

Areas for students to improve include:

• describing the behaviour of ductile materials in relation to the yield point.

Question 23(c)

In better responses, students were able to:

• recognise the relationship between increased second moment of area and resistance to bending of hollow tube.

Areas for students to improve include:

• identifying the effect of cross sectional shape of a material on its tensile, compressive and bending strength.

Question 24

In better responses, students were able to:

• outline a clear in-service advantage of the listed materials (a)
• realise that aluminium alloy may be heated to improve its malleability. Some mentioned recrystallisation temperature as a key factor in the process (b)
• use correct engineering terminology such as: malleable, die, ram, and hence illustrate that the metal takes up the cross-sectional shape of the die as it is forced through the die (b)
• correctly draw the half-sectional front view, including the representation of the screw thread and the four webs to AS1100 standards (c)
• show all relevant centre lines and not include hidden detail in the section half of the drawing.

Areas for students to improve include:

• recognising the difference between in-service properties and purely mechanical and/or physical properties (a)
• realising that extrusion is a solid forming process and that the metal was not molten when it was extruded (b).

Question 25

In better responses, students were able to:

• clearly describe, in some detail, the basic stages of jet propulsion, using an example such as a turbojet engine (a)
• explain, not simply describe, how the angle of attack influencing the lift generated by the wings, supporting their explanation by including details from one of the accepted theories of lift (b)
• draw a clearly labelled diagram that links to, supported and/or clarified their description or explanation of jet propulsion or angle of attack/lift (a and b)
• recognise the nature and direction of forces of flight and the conditions for equilibrium. From that they correctly calculated, either analytically or graphically, a missing force: drag (c)
• identify a variety of factors that might influence stress corrosion in aircraft panels or components (d).

Areas for students to improve include:

• developing an understanding of the factors affecting lift and induced drag, in flight related questions (b and c)
• utilising a force polygon sketch to clarify their calculations in a force equilibrium situation (c)
• identifying specific conditions for corrosion in aeronautical situations (d).

Question 26(a)

In better responses, students were able to:

• interpret the concept of compressive stress
• identify the correct formula to calculate area
• select a suitable formula and method to solve for the compressive stress
• use compatible SI units for stress.

Areas for students to improve include:

• calculating the cross-sectional area of the punch by using πD²/4
• converting orders of magnitude, for example, from MPa to Pa as Pascals specified in the answer line.

Question 26(b)

In better responses, students were able to:

• interpret the concept that friction is distributed around a circular shape
• identify the correct positioning of the friction force and the normal reaction
• use the correct formula to calculate the normal reaction.

Areas for students to improve include:

• manipulating the friction formula and the relative position of the friction and normal forces
• correctly understanding that the hole was circular and not treating the situation as having two sides.

Question 26(c)

In better responses, students were able to:

• recognise that moments calculations are the best method to solve for the required force
• resolve an angled force into two components
• determine the perpendicular distance to the line of action of the forces acting
• develop a balanced moment equation to calculate the required force.

Areas for students to improve include:

• using both x and y components of Q, with their correct distance in the moment calculation.

Question 26(d)

In better responses, students were able to:

• list relevant properties and then explain how each material is suitable for its use for the bearing retainer
• identify correct properties that are relevant for an engineer in selecting a material for this application.

Areas for students to improve include:

• providing a detailed comparison of the suitability of the two materials.

Question 27

In better responses, students were able to:

• determine the reactions on the beam and were able to plot Shear Force and Bending Moment diagrams. It should be noted that the Bending Moment diagram was more challenging (a)
• label all points on their graph which reinforced their understanding of the concepts (a)
• give specific examples and reasons to answer the question which they were able to expand out in a detailed response (b)
• understand that engineers used these diagrams to visually identify points of weakness or potential structural failure and then provided examples as to what an engineer could do to eliminate such problems. Examples included: material selection, size of members, redistributing loads, cost efficiency of redesigning members, and reinforcement (b).

Areas for students to improve include:

• avoiding reversal of the reactions. Some students reversed the reactions on the beam and plotted incorrect graphs according to their calculations (a)
• correctly labelling their graphs in case they have plotted the points inaccurately (a)
• deriving the Bending Moment diagram from the area under the Shear Force diagram; this is a simple and effective strategy for calculating bending moments (a)
• following guidelines, using the grid lines supplied and projecting down to plot their diagrams (a)
• explaining what the diagrams were and what information was obtained from them and providing reasons why an engineer would use them in the design of a project (b).