Engineering Studies 2019 HSC exam pack

Students should:

• know and use the key terms to access the full range of marks
• consider using graphical solutions if appropriate
• show full and clear working out for all questions involving calculations
• use correct terminology when describing/explaining engineering practices and concepts
• be comfortable in the manipulation of SI units and prefixes to arrive at the required units for the question
• 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 hydrofoil.

Question 21

In better responses, students were able to:

• identify the difference in breaking between toughened glass and soda lime glass (a)
• outline an advantage and relate this back to the properties of toughened glass (a)
• outline more than one property of toughened glass and how this was an advantage (a)
• identify that laminated timber can be manufactured to most shapes and sizes (b)
• identifying that they have greater specific strength than natural timber (b)
• identifying that knots and defects can be eliminated (b)
• describe a three-point bend or transverse test (c)
• provide a well-drawn and labelled diagram to support the description (c)
• correctly calculate the maximum bending stress using correct values and units (d)
• correctly find the value for ‘y’ – distance to the neutral axis (d).

Areas for students to improve include:

• correctly identify the properties of toughened versus laminated glasses (a)
• outlining properties of toughened glass with respect to the application, rather than addressing advantages of using glass over other general materials, such as steel (a)
• correctly identifying the different properties of laminated timber beams and plywood
• listing properties without justification (b)
• correctly qualifying strength characteristics (b)
• correctly identifying and describing correct testing procedures and not confusing correct test with a variety of other tests including hardness, impact, compression (showing UDL), and tensile tests (c)
• labelling sketches adequately (c)
• correctly identifying bending stress (c)
• correctly identifying the measurement and recording of deflection (c)
• understanding and using correct formula and substituting correct values (d)
• develop an understanding of correct distance to neutral axis (d)
• using correct values or units in their calculations.

Question 22

In better responses, students were able to:

• outline relevant responsibilities which were specific to the placement of the tower and not just general information about telecommunication towers and the role of engineers (a)
• explain in terms of the orientation of the repeaters in reference to increasing the distance and the strength of the signal for communication, relating it to reduced interference between the signals being received and transmitted (b)
• take moments about C to find the reaction at A. They were able to realise AC was a redundant member therefore determining N was equal to reaction A but opposite in nature (sense) (c)
• Some students were able to place a horizontal section plane through member M and then take moments about H to determine the value of M. Some students combined both graphical and analytical methods to calculate a correct value (c).

Areas for students to improve include:

• improving legibility and sentence structure of the answers (a)
• explaining the function the repeaters serve instead of primarily discussing the physical structure of the tower, how the load was positioned and why the supports were built that way (b)
• consider using graphical solutions (c)
• laying out their solution logically to ensure they do not become confused, for example when summing vertical and horizontal components (c)
• selecting the most appropriate point to take moments about, in this case it is H (c)
• ensuring answers are presented appropriately so that the marker can follow and interpret the methods being used (c).

Question 23

In better responses, students were able to:

• recognise the relationship between kinetic and potential energy at positions 1 and 2 (a)
• calculate the values of kinetic and potential energy correctly (a)
• differentiate between the value of the maximum height above the wall and the total height (a)
• identify the appropriate value of current from the data (b)
• use an appropriate method to calculate power (b)
• correctly demine the value for energy in kJ (b)
• apply the relevant formula to calculate the combined weight force of the rider and scooter (c)
• manipulate the given data and units correctly in calculations (c)
• subtract the weight of the rider to determine the scooter mass (c)
• recognise the need to increase the height of the scooter deck to improve rigidity (d)
• describe how the design modification increased the deck's resistance to bending (d)
• account for no change to overall mass as a result of the modification (d)
• provide a neat labelled sketch of the design modification (d).

Areas for students to improve include:

• manipulating equations to solve for an unknown (a)
• recognising that bodies can have both kinetic and potential energy (a)
• identifying current value from stated battery capacity (b)
• determining a resistance value to calculate power (b)
• understanding that pressure is a constant value (c)
• applying the correct cross-sectional area value for the weight force (c)
• accounting for separate components which comprise the total mass of an object (c)
• recognising that the bending strength of a structural member is related to the distance from outer surfaces to the neutral axis (d)
• stating reasons why a design modification would result in an increased resistance to deflection (d).

Question 24

In better responses, students were able to:

• use correct terminology (a)
• identify the differences in composites and metals (a)
• include an outline of a difference and/or similarity and related this back to the properties of the materials (a)
• outline several advantages/similarities and how each was an advantage (a)
• identify that there was pearlite and ferrite in the microstructure (bi)
• represent clearly smaller grain structure in the normalised microstructure (bi)
• correctly label the pearlite eutectoid structure and the ferrite structure (bi)
• identify that the smaller grain structure made the normalised steel stronger (bii)
• identify that both equi-axed grains and the removal of stress points resulting from the normalisation process increased the strength of the steel (bii)
• demonstrate the knowledge to correctly produce all three diagrams with correct calculations (c)
• demonstrate vertical projection between the three diagrams (c).

Areas for students to improve include:

• knowledge of what constitutes a composite material (a)
• understanding the characteristics of composites (a)
• understanding how to draw a microstructure for a hypo-eutectoid steel (bi)
• using accepted standard conventions of representing microstructures (bi)
• labelling the grains that make up the microstructure (bi)
• better representing the smaller grain structure resulting from normalised process (bi)
• identifying and responding to what the question is asking, that is, ‘how’ the process of normalising makes the steel more suitable (bii)
• understanding the impact of the process of normalising on steel (bii)
• understanding the impact of smaller grain size has on the steel (bii)
• producing a free body diagram from the space diagram with ALL relevant information (c)
• using vertical projection to transfer the forces to the diagrams (c)
• demonstrating an understanding of the free body not extending the full width of the wing structure (c)
• using a correct calculation method for bending moment at various point along the beam (c).

Question 25

In better responses, students were able to:

• recognise/explain that drag opposes forward motion and therefore must be reduced as much as possible (a)
• apply aeronautical principles (fluid mechanics) such as aerodynamic drag, thrust and lift to the hydrodynamic case of yacht hulls (a)
• suggest design improvements such as streamlining, smoothing surfaces, material selection, reduction of surface area, use of a winged keel with reference to a yacht hull (a)
• recognise that Kevlar is a woven fabric and is not itself a composite material (b)
• provide suitable properties that make the material suitable for use both in yachts and aircraft (b)
• explain why engineers use CAD rather than list aspects of CAD (c)
• transfer their understanding of lift in aircraft wings to the lift provided by a hydrofoil, that is aerodynamics and hydrodynamics apply the same principles of fluid mechanics (d)
• supply a full explanation of Bernoulli’s and/or Newton’s theories as producers of lift (d).

Areas for students to improve include:

• transfer of knowledge of aerodynamic principles to hydrodynamics (a)
• knowledge of the properties of Kevlar fibre, carbon fibre/epoxy composites and aluminium alloys as they relate to applications in yachts and aircraft (b)
• explaining why engineers use CAD rather than just providing a list of advantages of CAD over traditional drafting methods (c)
• explaining how a hydrofoil provides lift, providing a clear and succinct explanation of the similarity of a hydrofoil to an aerofoil with a link to and outline of Bernoulli’s principle and/or Newtons theories as explanations of lift (d)
• explain how lifting the board out of the water reduces drag (d).

Question 26

In better responses, students were able to:

• demonstrate a good understanding of magnetic induction as a result of converting mechanical energy into electrical energy (a)
• succinctly explain how a generator converts mechanical energy into electrical energy (a)
• articulate functional properties of circuit components in an AM radio receiver (bi)
• use appropriate functions and terms to describe simple circuit components (bi)
• demonstrate the function of individual components in a simple circuit receiver (bi)
• interpret and draw AM radio receiver capacitor waveforms (bii)
• identify the correct waveform depending on position in a simple circuit (bii)
• articulate and explain the relationship of high impedance in order to produce an audible signal in an AM receiver (biii)
• comprehensively link a relevant formula to support explanation of high impedance in a speaker (biii).

Areas for students to improve include:

• associating a rotating magnet within a coil of wire with generating electricity (a)
• identifying the process of magnetic induction and the concepts/processes required to produce electricity (a)
• recognising specific function(s) of circuit component(s) in a simple AC radio receiver (bi)
• identifying key functions of a circuit component and its significance in an AM radio (bi)
• identifying the correct waveform depending on the functionality of the signal diode and capacitor types (fixed/variable) (bii)
• interpreting and drawing appropriate waveforms in correct circuit position (bii)
• interpreting and drawing positive demodulated and half wave forms (bii)
• providing a clear connection between high resistance and low current in order for a voltage to achieve an audible signal in the speaker (biii)
• understanding that power is achieved by the collection of an electromagnetic signal in the circuit (biii)
• providing a relevant formula to support their answer (biii).

Question 27

In better responses, students were able to:

• identify types of detail drawings then relate those to aspects of design and manufacturing (a)
• understand the concept of double shear when calculating the diameter of the pin (bi)
• draw a section view of the top of the bracket and pin using AS1100 conventions (bii).

Areas for students to improve include:

• understanding types of detail drawings available to designers and manufacturers (a)
• understanding the concept of double shear (bi)
• using appropriate data for calculations involving double shear (bi)
• drawing with AS1100 conventions including centre lines and hidden detail (bii).