SmarterEd

Aussie Maths & Science Teachers: Save your time with SmarterEd

ENGINEERING, AE 2018 HSC 6 MC

Which device is used to measure the airspeed of an aircraft in flight?

  1. Altimeter
  2. Pitot tube
  3. Wind gauge
  4. Potentiometer
Show Answers Only

`B`

Show Worked Solution
  •  Pitot tubes measure airspeed by comparing static and dynamic pressure, therefore `B` is correct.
  •  Altimeters measure altitude, wind gauges measure wind and potentiometers are a type of resistor.

`=>B`

ENGINEERING, TE 2020 HSC 26b

Outline benefits of digital signal transmission.   (3 marks)

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Benefits of digital signal transmission include:

  • Immunity to transmission noise and interference (clearer signal)
  • Signal can be boosted or regenerated along the transmission path (reduced attenuation)
  • Can be encrypted to be kept secure and private
  • Signals can be processed and multiplexed (multiple messages can be sent along the same channel simultaneously)
  • Error detection and correction is possible
  • Cheaper than analogue transmission
  • Signal can be compressed
  • Signal can be stored and further processed
Show Worked Solution

Benefits of digital signal transmission include:

  • Immunity to transmission noise and interference (clearer signal)
  • Signal can be boosted or regenerated along the transmission path (reduced attenuation)
  • Can be encrypted to be kept secure and private
  • Signals can be processed and multiplexed (multiple messages can be sent along the same channel simultaneously)
  • Error detection and correction is possible
  • Cheaper than analogue transmission
  • Signal can be compressed
  • Signal can be stored and further processed

ENGINEERING, CS 2018 HSC 27b

Why would an engineer refer to shear force diagrams and bending moment diagrams when determining the effects of loads on a beam?   (4 marks)

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  • Shear force and bending moment diagrams are graphs used together with structural analysis to assist engineers in the structural design process.
  • They help quantify the size of shear forces and bending moments on a structural element, such as a beam, at a given point, so possible weaknesses in the element can be determined.
  • They are used to establish the size, type and material of a beam in a structure so that support can be provided without structural failure.
  • So SF and BM diagrams help structural engineers decide the geometry and material of design elements.
Show Worked Solution
  • Shear force and bending moment diagrams are graphs used together with structural analysis to assist engineers in the structural design process.
  • They help quantify the size of shear forces and bending moments on a structural element, such as a beam, at a given point, so possible weaknesses in the element can be determined.
  • They are used to establish the size, type and material of a beam in a structure so that support can be provided without structural failure.
  • So SF and BM diagrams help structural engineers decide the geometry and material of design elements.

ENGINEERING, CS 2018 HSC 27a

A 6-metre beam is loaded as shown.
 

On the following page, draw the shear force and bending moment diagrams. Support your answer with relevant calculations. Ignore the weight of the beam.

Space for calculations is provided below.   (6 marks)
 

Show Answers Only

“

Show Worked Solution

`text{Shear Force calculations:}`

`text{SF}_1=+↑ SigmaF = 16\ text{kN}`

`text{SF}_2=+↑ SigmaF = 16-15 = 1\ text{kN}`

`text{SF}_3=+↑ SigmaF = 16-15-12 = -11\ text{kN}`
 

`text{Bending Moment calculations:}`

`text{BM}_1=+↓ SigmaM = 16 xx 2=32\ text{kNM}`

`text{BM}_2=+↓ SigmaM = 16 xx 3-15xx1=48-15=33\ text{kNM}`

`text{BM}_3=+↓ SigmaM = 16 xx 6-15xx4-12xx3=96-60-36=0\ text{kNM}`

 

ENGINEERING, PPT 2018 HSC 26d

The components of the bearing assembly used in the fidget spinner are shown.
 

The retainer can be made from either glass fibre-reinforced nylon or stainless steel.

Compare the in-service properties of these materials for use in the retainer.   (4 marks)

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Show Worked Solution

ENGINEERING, CS 2018 HSC 26a

A fidget spinner is shown. It is a toy that contains a ball bearing in its centre and is designed to spin on its axis with little effort.
 

The central components of a fidget spinner are press fitted together using a press punch.
 

The press punch diameter is 21 mm. The force applied by the press punch to the bearing is 17.3 N.

Calculate the compressive stress in the press punch.   (2 marks)

Show Answers Only

`50\ 000\ text{Pa}`

Show Worked Solution
`F` `=17.3\ text{N}`  
`a` `=(pi xx 21^2)/4=346\ text{mm}^2=0.000346\ text{m}^2`  

 
`sigma=F/a=17.3/0.000346=50\ 000\ text{Pa}`

ENGINEERING, AE 2018 HSC 25d

Identify factors that contribute to stress corrosion cracking in aluminium alloy aircraft components.   (2 marks)

Show Answers Only
  • Stress corrosion cracking develops in a corrosive environment (moisture).
  • Sustained tensile stress is also a contributing factor and can be applied both externally or internally through residual tensile stress.
Show Worked Solution
  • Stress corrosion cracking develops in a corrosive environment (moisture).
  • Sustained tensile stress is also a contributing factor and can be applied both externally or internally through residual tensile stress.

ENGINEERING, AE 2018 HSC 25c

 A two-engine aircraft with mass 330 tonnes is climbing at 15°. Each engine produces 510 kN of thrust. The aircraft maintains a constant velocity.

  1. Complete the space diagram by indicating the four key forces of flight for this situation.   (2 marks)
     
     

  1. Determine the induced drag force for this situation.   (3 marks)
Show Answers Only

i.

ii.   `166\ text{kN}`

Show Worked Solution

i.

ii.  `text{Find Induced drag} (D):`

`text{Weight}\ (W)=text{m} xx text{g}=330 xx 10^3 xx 10=33 xx 10^5\ text {N}`

`text{Thrust}\ (T)=510 xx 10^3 xx 2=102 xx 10^4\ \text{N}`

`T` `= D + W\ sin\ gamma`  
`D` `= T-W\ sin\ gamma`  
  `=102 xx 10^4  –  33 xx 10^5\ sin15^\circ`  
  `=165\ 897.1512`  
  `=166 xx 10^3`  
  `=166\ text{kN}`  

♦♦ Mean mark (ii) 34%.

ENGINEERING, AE 2018 HSC 25a

Describe the basic operational principles of jet propulsion. Use a labelled sketch to support your answer.   (3 marks)

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  • Intake air is compressed to a point where it’ s temperature is greater than the ignition point of the fuel.
  • The combustion chamber receives the atomised fuel and through expansion generates a higher velocity gas.
  • Thrust is generating when the high velocity gas is expelled through the exhaust.

 

Show Worked Solution
  • Intake air is compressed to a point where it’ s temperature is greater than the ignition point of the fuel.
  • The combustion chamber receives the atomised fuel and through expansion generates a higher velocity gas.
  • Thrust is generating when the high velocity gas is expelled through the exhaust.
     

ENGINEERING, PPT 2018 HSC 24c

An exploded view of an adjustable scaffold foot is shown.
 

 

On the next page, complete a half-sectioned front view of the scaffold foot with the jack nut arm. The arrow indicates the direction of viewing.   (6 marks)
 

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Show Worked Solution

ENGINEERING, PPT 2018 HSC 24b

The cross-section of an extruded aluminium alloy plank is shown.
 

Outline the steps of the extrusion process.   (2 marks)

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The extruded aluminium plank is made by:

  • Heating an aluminium billet (heat > recrystallisation temperature).
  • Forcing the billet through a heated die to make the necessary cross-section.
Show Worked Solution

The extruded aluminium plank is made by:

  • Heating an aluminium billet (heat > recrystallisation temperature).
  • Forcing the billet through a heated die to make the necessary cross-section.
Mean mark 56%.

ENGINEERING, CS 2018 HSC 24a

The diagram shows a scaffold supporting planks. The planks can be made from laminated timber, aluminium alloy or galvanised steel.
 

Outline an in-service advantage of each of these materials when used as a scaffold plank.   (3 marks)

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Answers could include one advantage from each material type below:

Laminated timber plank

  • Easily cut on-site to accommodate a non-standard opening.
  • Non-conductive.

Aluminium scaffold plank

  • Low density
  • Light weight makes aluminium planks easy to manoeuver on-site.

Galvanised steel planks

  • Can absorb energy through impact without shattering or fracturing (high impact resistance).
  • Appropriate for applications where the scaffold is likely to be exposed to falling loads eg concrete block laying, bricklaying, concreting and demolition work.
Show Worked Solution

Answers could include one advantage from each material type below:

Laminated timber plank

  • Easily cut on-site to accommodate a non-standard opening.
  • Non-conductive.

Aluminium scaffold plank

  • Low density
  • Light weight makes aluminium planks easy to manoeuver on-site.

Galvanised steel planks

  • Can absorb energy through impact without shattering or fracturing (high impact resistance).
  • Appropriate for applications where the scaffold is likely to be exposed to falling loads eg concrete block laying, bricklaying, concreting and demolition work.

ENGINEERING, TE 2018 HSC 22a

Telecommunication signals can be carried by a variety of transmission media. A common form of connection between a television set and an antenna is a coaxial cable.
 

Why is copper-coated steel used for the central wire?   (2 marks)

Show Answers Only
  • Steel provides tensile strength.
  • Electrical conductivity is provided by the copper.
Show Worked Solution
  • Steel provides tensile strength.
  • Electrical conductivity is provided by the copper.
Mean mark 56%.

ENGINEERING, PPT 2018 HSC 21c

The self-driving vehicle has a mass of 1.5 tonnes and is travelling at 60 km/h.

Calculate its kinetic energy.   (3 marks)

Show Answers Only

`208.4\ text{kJ}`

Show Worked Solution

`text{Converting km/h to m/second:}`

`v=60\ text{km/h}=(60\ 000)/3600\ text{m/s}= 16.67\ text{m/s}`

`m=1.5\ text{tonnes} =1500\ text{kg}`

`KE` `=1/2mv^2`  
  `=1/2 xx 1500 xx 16.67^2`  
  `=208\ 416.675\ text{J}`  
  `=208.4\ text{kJ}`  

ENGINEERING, CS 2018 HSC 1 MC

An engineer has been asked to investigate and report on the failure of a component.

Which row of the table correctly identifies what the engineer would need to do before finalising the report?
 

Show Answers Only

`B`

Show Worked Solution
  •  The purpose of the report is to investigate and report on the failure of a component.
  •  This does not include redesigning the component as a new design has nothing to do with why a previous iteration failed.

`=>B`

ENGINEERING, AE 2017 HSC 26b

Orthogonal and pictorial drawings of a sheet metal electrical cable cover are given below.
 

  1. Draw a half-development of the electrical cable cover. Use the centre line to position the development.   (4 marks)
     

  1. A 20 mm diameter hole is to be punched through the top of the electrical cable cover before folding.
  2. The ultimate shear stress of the material used to manufacture the cover is 110 MPa.
  3. Calculate the force required to punch out the hole if the thickness of the sheet metal is 0.5 mm.   (3 marks)
Show Answers Only

i.   
         

ii.   `3.46\ text{kN}`

Show Worked Solution

i.   
         

Key Points for this Drawing:

  • Find true length of each line from the diagrams given
  • Do not dimension
  • Only complete a half development, not a full development
  • Use lighter lines for the the bends/folds and heavier lines for the outline
  • Label all points
ii.    `delta_S` `=F_S/A_S`
  `F_S` `=delta_S xx A_S`

 
`A_S = pid xx t=pi xx 20 xx 0.5 = 31.4\ text{mm}^2`

`:.F_S= 110 xx 31.4=3455.7\ text{N}=3.46\ text{kN}`


♦ Mean mark (ii) 42%.

BIOLOGY, M5 2018 HSC 26a

Compare proteins and polypeptides.   (2 marks)

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Proteins and Polypeptides

  • Both composed of amino acids
  • Polypeptides are single chain amino acids coded for a single gene (not folded and non-functional).
  • Proteins are composed of one or more polypeptides (folded and functional).
Show Worked Solution

Proteins and Polypeptides

  • Both composed of amino acids
  • Polypeptides are single chain amino acids coded for a single gene (not folded and non-functional).
  • Proteins are composed of one or more polypeptides (folded and functional).

ENGINEERING, PPT 2017 HSC 23c

The U-bolt clamp shown is used to hold a Ø42 digital TV aerial pipe in place.

Draw an assembled half-sectional front view of this U-bolt clamp to AS 1100 standards. The front is indicated by the direction of the arrow.

Use a scale of 2 : 1 and place the half section on the right-hand side.   (6 marks)
 

 

 

Show Answers Only

Show Worked Solution

The AS 1100 drawing reflects the correct scale, but we note exact measurements are required for the exam diagram.

Key Points for this Drawing:

  • There is very little actual sectioning in this drawing as it is being used to test if students know what to section. DO NOT section nuts, bolts or threads.
  • The small rectangle is the only part sectioned as it the only part cut that is not a nut, bolt or thread.
  • Although only 1 nut is shown the instructions say to draw both.
  • Use correct bolt dimensions for nut size.
  • Do not dimension unless asked.
  • Do not show hidden detail on sectioned side.
  • Sectioning lines should be on a 45 degree angle and 3 mm apart.
Mean mark 59%.

BIOLOGY, M7 2017 HSC 22b

Explain how TWO different methods used to treat drinking water reduce the risk of infection.   (4 marks)

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  • Filtration and chlorination are two effective methods that materially reduce the risk associated with drinking water contaminants.
  • Filtration removes pathogens which reduces the risk of infection by preventing them from passing through the filter.
  • Chlorine kills pathogens before the water reaches humans thereby reducing the risk  of disease and infection.
Show Worked Solution
  • Filtration and chlorination are two effective methods that materially reduce the risk associated with drinking water contaminants.
  • Filtration removes pathogens which reduces the risk of infection by preventing them from passing through the filter.
  • Chlorine kills pathogens before the water reaches humans thereby reducing the risk  of disease and infection.

BIOLOGY, M7 2018 HSC 22a

Pasteur performed an experiment to identify the role of microbes in decay.

Justify a conclusion that can be drawn from his results.  (2 marks)

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Pasteur’s swan-neck flask experiment

  • The straight necked flask became contaminated after a few days, whereas, the sterile swan-neck flask confined the germs in the curved section of the neck and no contamination occurred.
  • This proved that microbes are produced from pre-existing microbes and not from the air itself.
Show Worked Solution

Pasteur’s swan-neck flask experiment

  • The straight necked flask became contaminated after a few days, whereas, the sterile swan-neck flask confined the germs in the curved section of the neck and no contamination occurred.
  • This proved that microbes are produced from pre-existing microbes and not from the air itself.

♦ Mean mark (b)(i) 41%.

Mean mark (b)(ii) 51%

ENGINEERING, CS 2017 HSC 27a

Why is the routine testing of engineering components important during service?   (2 marks)

Show Answers Only
  • Aircraft jet engines, diesel trucks, structural beams and a myriad of other engineering components are subject to heavy loads, polluted and corrosive environments, and high operating cycles.
  • It is important to maintain regular routine testing to help guarantee that dangerous conditions or possible faults do not occur.
  • This type of testing has a key role in safeguarding the public as well as increasing the longevity and economic benefit of engineering components.
Show Worked Solution
  • Aircraft jet engines, diesel trucks, structural beams and a myriad of other engineering components are subject to heavy loads, polluted and corrosive environments, and high operating cycles.
  • It is important to maintain regular routine testing to help guarantee that dangerous conditions or possible faults do not occur.
  • This type of testing has a key role in safeguarding the public as well as increasing the longevity and economic benefit of engineering components.
Mean mark 59%.

ENGINEERING, AE 2017 HSC 26a

The flaps of an executive jet are controlled using a hydraulic system. A force of 1 kN acts on the 40 mm diameter master piston.
 

What force would need to be developed to move the flap if the slave piston has a diameter of 100 mm?   (3 marks)

Show Answers Only

`6.25\ text{kN}`

Show Worked Solution

`P=F/A`

`1000/(pi xx 20^2)` `=F_S/(pi xx 50^2)`  
`F_S` `=(1000 xx pi xx 50^2)/(pi xx 20^2)=6250\ text{N}=6.25\ text{kN}`  

ENGINEERING, CS 2017 HSC 25a

A pin-jointed truss designed to support a roadside sign is shown.
 

  1. Determine the magnitude and direction of the reactions at `A` and `B`.   (4 marks)
  1. Determine the magnitude and nature of the force in member `C`.   (2 marks)
  1. Explain why concrete would be a suitable material to support the roadside sign around point `D`.   (2 marks)
Show Answers Only

i.   `R_B=37\ text{N} larr`

`R_A=44.7\ text{kN}, \ theta=26.6^(@)` 

ii.   `F_C=17\ text{kN (compression)}`
iii.   Suitability of concrete

  • Easily poured and formed around the sign.
  • Relatively quick to cure.
  • Weather resistant.
  • Hardens and sets with high strength and hardness.
Show Worked Solution

\[\textbf{i}. \ \ \ce{->[\ce{+}]} \sum M_A = 0 \]

`3xx1.5-20 xx3+R_(B)xx1.5=0`

`4.5-60+1.5R_(B)=0`

`1.5R_(B)` `=55.5`  
`R_(B)` `=(55.5)/(1.5)=37\ text{N} larr`  

  

Mean mark 56%.

`uarr sumF_(V)=0`

`R_(AV)=20\ text{kN} +uarr`

\[\ce{->[\ce{+}]} \sum F_H = 0 \]

`R_(AH)=37+3=40\ text{kN} rarr^(+)`

`R_A=sqrt(20^(2)+40^(2))=sqrt2000=44.7\ text{kN}`

`tan\  theta` `=(R_(AV))/(R_(AH))=20/40=0.5`  
`:.theta` `=26.6^(@)`  

 

\[\textbf{ii}. \]

`text{Taking moments about X:}`

\({+ \circlearrowleft} \Sigma M_X = 0\)

`0` `=-1.5 xxF_(C)+1.5 xx20-1.5 xx3`  
`0` `=-F_(C)+20-3`  
`F_(C)` `=17\ text{kN (compression)}`  

♦♦ Mean mark (ii) 38%.

iii.   Suitability of concrete

  • Easily poured and formed around the sign.
  • Relatively quick to cure.
  • Weather resistant.
  • Hardens and sets with high strength and hardness.

♦ Mean mark (iii) 52%.

ENGINEERING, PPT 2017 HSC 24b

A child and sled with a combined mass of 23 kg are being pulled along a horizontal snow-covered surface using a rope.
 

The coefficient of static friction between the sled and the snow is 0.14.

  1. Draw a free-body diagram that indicates the forces acting on the sled. Label the diagram.   (2 marks)
  1. Calculate the tension in the rope immediately before the point at which the sled and child begin to move.   (3 marks)
Show Answers Only

i.
       

 

ii.   `text{32 N}`

Show Worked Solution
i.
       

Mean mark (i) 57%.

ii.   `text{Weight}\ = mg = 23 xx 10 = 230\ text{N}`     

`text{Solving for}\ T:`

`tan^(-1)(0.14) = 8°`

`text{Using the sine rule:}`

`T/(sin8°)` `=230/(sin92°)`  
`T` `=(230 xx sin8°)/(sin92°)=32.0\ text{N}`  

  
`:.\ text{Tension in the rope = 32 N}`


♦ Mean mark (ii) 40%.

ENGINEERING, PPT 2017 HSC 24a

Sleds are used to slide loads over soft surfaces such as grass, sand and snow. They can be made using polypropylene.

  1. Explain how the properties of polypropylene make it a suitable material for this application.   (3 marks)
  1. Describe a suitable manufacturing method to make a sled from polypropylene.   (3 marks)
Show Answers Only

i.   Polypropylene properties

  • Low coefficient of friction, lightweight and durable with excellent flexural strength.
  • In the manufacturing process, polypropylene is a good material for injection moulding which makes it easy to produce. 

ii.  Manufacturing method:

  • Polymer pellets are introduced into an injection moulding machine.
  • A heating unit surrounding the exterior of the machine and internal friction heat the pellets.
  • They are forced into a steel mould under pressure.
  • After solidifying, the mould halves are separated and removed using injector pins.
  • Cooling, removal of surplus flash and polishing complete the process.
Show Worked Solution

i.   Polypropylene properties

  • Low coefficient of friction, lightweight and durable with excellent flexural strength.
  • In the manufacturing process, polypropylene is a good material for injection moulding which makes it easy to produce.

ii.  Manufacturing method:

  • Polymer pellets are introduced into an injection moulding machine.
  • A heating unit surrounding the exterior of the machine and internal friction heat the pellets.
  • They are forced into a steel mould under pressure.
  • After solidifying, the mould halves are separated and removed using injector pins.
  • Cooling, removal of surplus flash and polishing complete the process.

♦ Mean mark (ii) 53%.

ENGINEERING, TE 2017 HSC 23a

A digital TV receiver circuit uses logic gates as shown.
 

Complete the truth table for this logic circuit.   (2 marks)
 

Show Answers Only

\begin{array} {|c|c|c|}
\hline \ \text{A}\ & \text{B}\ & \text{Z}\ \\
\hline \ \ \ \ 0\ \ \ \  & \ \ \ \ 0 \ \ \ \ & \ \ \ \ 1\ \ \ \ \  \\
\hline \ 0 & 1 & 0 \\
\hline \ 1 & 0 & 0 \\
\hline \ 1 & 1 & 0 \\
\hline \end{array}

Show Worked Solution

\begin{array} {|c|c|c|}
\hline \ \text{A}\ & \text{B}\ & \text{Z}\ \\
\hline \ \ \ \ 0\ \ \ \  & \ \ \ \ 0 \ \ \ \ & \ \ \ \ 1\ \ \ \ \  \\
\hline \ 0 & 1 & 0 \\
\hline \ 1 & 0 & 0 \\
\hline \ 1 & 1 & 0 \\
\hline \end{array}

ENGINEERING, CS 2017 HSC 22d

When a bike goes over a bump, there is a vertical force of 3 kN exerted axially on the main pillar.
 

The cross-section of the pillar is shown.
 

Calculate the compressive stress acting in the pillar.   (3 marks)

Show Answers Only

`15.9\ text{MPa}`

Show Worked Solution
`text{CSA}` `=(pi(d_1)^2)/4-(pi(d_2)^2)/4`  
  `=pi/4(32^2 – 28^2)`  
  `=(240pi)/4`  
  `=188.5\ text{mm}^2`  

 
`sigma_c=F/A=3000/188.5=15.9\ text{MPa}`

ENGINEERING, PPT 2017 HSC 22c

A bike with a rider rolls down a hill without braking from a standing start at point `A`.
 

The combined weight of the bike and the rider is 100 kg.

Calculate the speed of the rider at point `B`. (Assume no wind resistance and 100 % efficiency.)   (2 marks)

Show Answers Only

`20\ text{m/s}`

Show Worked Solution

`KE_text(bottom) = PE_text(top)`

`1/2 mv^2` `=mgh`  
`v^2` `=2gh`  
`v` `=sqrt(2xx10xx20)`  
  `=sqrt(400)`  
  `=20\ text{m/s}`  
Mean mark 58%.

ENGINEERING, PPT 2017 HSC 22a

Carbon fibre was originally developed to produce aircraft bodies and high performance vehicles. Carbon fibre is now used in a wide range of applications, including the manufacture of the type of bicycle frame shown.
 

Outline the advantages of carbon fibre bicycle frames over steel bicycle frames.   (3 marks)

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Advantages of carbon fibre bicycle frames

  • Excellent strength to weight ratio, which is a preferred feature and is superior to that of steel.
  • More intricate shapes can be moulded with carbon fibre than steel.
  • Rigid and resistant to corrosion.
  • Wide colour selection available.
Show Worked Solution

Advantages of carbon fibre bicycle frames

  • Excellent strength to weight ratio, which is a preferred feature and is superior to that of steel.
  • More intricate shapes can be moulded with carbon fibre than steel.
  • Rigid and resistant to corrosion.
  • Wide colour selection available.

ENGINEERING, PPT 2017 HSC 21a

Using examples, explain why gears are used in the design of vehicles.   (3 marks)

Show Answers Only
  • Speed, rotation direction and torque can all be changed in engineering mechanisms using gears.
  • Different gear ratios with different types of gears can be combined to change direction or increase torque or speed.
  • For example, a truck cannot travel fast but it can carry tonnes of goods, whereas a performance motorcycle is unable to carry any meaningful load but can travel at high speeds.
Show Worked Solution
  • Speed, rotation direction and torque can all be changed in engineering mechanisms using gears.
  • Different gear ratios with different types of gears can be combined to change direction or increase torque or speed.
  • For example, a truck cannot travel fast but it can carry tonnes of goods, whereas a performance motorcycle is unable to carry any meaningful load but can travel at high speeds.

ENGINEERING, PPT 2019 HSC 27bii

An assembly drawing of a bracket and lock pin with the flange removed is shown.
 

Using the starting lines and centre mark provided, draw a fully sectioned top view, to AS 1100 drawing standards. The section plane passes through the centre of the mounting holes. Use the dimensions on the drawing and the lock pin diameter determined in part (b)(i). Use a scale of 1:2.   (3 marks)
 

Show Answers Only

Show Worked Solution

ENGINEERING, AE 2018 HSC 12 MC

A transition piece is shown.
 

Which of the following correctly represents the development of the transition piece?
 

 

Show Answers Only

`A`

Show Worked Solution
  • As shown in the diagram, the longer ends of W, X, Y and Z are all at the same end of the piece.
  • A is the only answer which suits this criteria.

`=>A`

ENGINEERING, TE 2022 HSC 22d

An orthogonal view of a smart watch is shown.
 

Construct a freehand pictorial sketch of the smart watch as viewed in the direction of the arrow.   (3 marks)

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Notes on this drawing:

  • Ensure correct viewing direction
  • Freehand sketch does not require instruments
  • Do not dimension or show hidden detail
  • Provide basic shape and important features with relatively straight lines
  • Ensure correct scale is used
Show Worked Solution

Notes on this drawing:

  • Ensure correct viewing direction
  • Freehand sketch does not require instruments
  • Do not dimension or show hidden detail
  • Provide basic shape and important features with relatively straight lines
  • Ensure correct scale is used

BIOLOGY, M6 2021 HSC 33b

Genetically engineered Atlantic salmon have been produced and approved for aquaculture in the US.

The graph summarises the growth of standard salmon and transgenic salmon.
 


  1.  
    Explain ONE potential benefit of using transgenic salmon in aquaculture. Support your answer with data from the graph.   (3 marks)

Show Answers Only
  • The graph shows that transgenic salmon grow faster than standard salmon in the first two years.
  • Consequently, they reach market size 5 months earlier than standard salmon.
  • This saves money in producing fish for market size as there are lower food and maintenance costs.
Show Worked Solution
  • The graph shows that transgenic salmon grow faster than standard salmon in the first two years.
  • Consequently, they reach market size 5 months earlier than standard salmon.
  • This saves money in producing fish for market size as there are lower food and maintenance costs.

ENGINEERING, PPT 2019 HSC 26a

The photograph shows an AM radio coupled to a pedal-powered generator. This radio allowed communication in remote areas of Australia during the 1920s.
 

Explain how the mechanical energy from pedalling was converted into electrical energy in the generator to power the AM radio.   (3 marks)

Show Answers Only
  • A generator consists of a magnet surrounded by a coil of wire.
  • Pedalling causes the magnet to spin and electricity is produced within the coil through magnetic induction.
  • The radio transceiver is powered by the generated electrical energy.
  • As the generator’s speed increases so does the voltage supplied.
Show Worked Solution
  • A generator consists of a magnet surrounded by a coil of wire.
  • Pedalling causes the magnet to spin and electricity is produced within the coil through magnetic induction.
  • The radio transceiver is powered by the generated electrical energy.
  • As the generator’s speed increases so does the voltage supplied.

ENGINEERING, AE 2019 HSC 25d

The photograph shows a board with a hydrofoil attached underneath.

The hydrofoil is used to lift the board out of the water as the rider is towed behind a boat at high speed.

Explain why the hydrofoil can lift the board out of the water when it is travelling at high speed.   (3 marks)

Show Answers Only
  • Water flows around and over the board as it moves forwards.
  • A difference in pressure is created above (low pressure) and below (high pressure) the hydrofoil due to its shape.
  • The board lifts upwards due to the higher pressure created by the hydrofoil from under the board.
  • The deflection of water downwards also creates lift (an upward reaction force) at the trailing edge.
  • The board is lifted out of the water once a critical speed is reached.
Show Worked Solution
  • Water flows around and over the board as it moves forwards.
  • A difference in pressure is created above (low pressure) and below (high pressure) the hydrofoil due to its shape.
  • The board lifts upwards due to the higher pressure created by the hydrofoil from under the board.
  • The deflection of water downwards also creates lift (an upward reaction force) at the trailing edge.
  • The board is lifted out of the water once a critical speed is reached.

ENGINEERING, AE 2019 HSC 25c

An intricate component used on racing yachts is shown below being modelled using computer-aided drawing (CAD) software.
 

Explain why engineers use CAD software to design and model intricate components.   (3 marks)

Show Answers Only
  • CAD can produce multiple immediate outputs, such as a 3D depiction, a visual image, finite element analysis and hardcopy printing.
  • Drawings are easily modified.
  • Files can be shared collaboratively.
  • Amendments can be immediately applied to any related documents.
Show Worked Solution
  • CAD can produce multiple immediate outputs, such as a 3D depiction, a visual image, finite element analysis and hardcopy printing.
  • Drawings are easily modified.
  • Files can be shared collaboratively.
  • Amendments can be immediately applied to any related documents.

ENGINEERING, AE 2019 HSC 25b

Some materials have properties that allow them to be used in the manufacture of both modern racing yachts and aircraft. These materials include Kevlar® aramid fibre, carbon fibre epoxy composites and aluminium alloys.

Complete the table by providing a property which makes each of these materials suitable for the manufacture of both yachts and aircraft.   (3 marks)
 

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Include one of the properties in the second column:

Show Worked Solution

Include one of the properties in the second column:

ENGINEERING, AE 2019 HSC 25a

Modern racing yachts are now designed using aeronautical engineering principles.

   

The diagram shows the hull of a racing yacht.
 

How can engineers use an understanding of the effects of drag to improve the design of racing yacht hulls?   (3 marks) 

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  • Drag minimisation leads to increased speeds as maximum forward thrust can be achieved.
  • Streamlining the hull leads to less countercurrents (vortices).
  • Surfaces with a high sheen minimise drag.
  • The use of lightweight construction materials creates less drag.
Show Worked Solution
  • Drag minimisation leads to increased speeds as maximum forward thrust can be achieved.
  • Streamlining the hull leads to less countercurrents (vortices).
  • Surfaces with a high sheen minimise drag.
  • The use of lightweight construction materials creates less drag.

ENGINEERING, AE 2019 HSC 24a

An image of an aeroplane is shown with the position of the wing support beam indicated.
 

Assume the engines are supported by the single beam. The beam runs through the plane, wing tip to wing tip.

Compare the use of composite materials with the use of metals for the manufacture of the beam.   (3 marks)

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Answers could include 3 of the following comparisons:

Composite materials vs Metals 

  • Composite materials are lighter than metals.
  • Manufacture: Carbon fibre epoxy composite beams requires specialised equipment whereas metal based inputs can be manufactured using readily accessible tools such as welders, gas torches and plasma cutters.
  • Composite materials are easier to lift due to lighter weight. This allows workers to position them more easily during the construction process.
  • Equipment used for making carbon fibre epoxy moulds likely to be more accurate than in metal fabrication. However, it is possible to achieve similar accuracy in machining metals compared to that of composite materials.
  • Due to the nature of the wing support beam and the stresses placed on it, a metal beam is subject to stress weaknesses (such as scratches and corners of drilled holes) and flaws in welds that create fatigue. Carbon fibre not affected by fatigue cracking.
Show Worked Solution

Answers could include 3 of the following comparisons:

Composite materials vs Metals 

  • Composite materials are lighter than metals.
  • Manufacture: Carbon fibre epoxy composite beams requires specialised equipment whereas metal based inputs can be manufactured using readily accessible tools such as welders, gas torches and plasma cutters.
  • Composite materials are easier to lift due to lighter weight. This allows workers to position them more easily during the construction process.
  • Equipment used for making carbon fibre epoxy moulds likely to be more accurate than in metal fabrication. However, it is possible to achieve similar accuracy in machining metals compared to that of composite materials.
  • Due to the nature of the wing support beam and the stresses placed on it, a metal beam is subject to stress weaknesses (such as scratches and corners of drilled holes) and flaws in welds that create fatigue. Carbon fibre not affected by fatigue cracking.

ENGINEERING, PPT 2019 HSC 23a

A scooter and rider enter the half pipe shown at a velocity of 3 m/s. The scooter and rider have a combined mass of 55 kg.
 

Calculate the maximum height, `h`, the scooter and rider will reach above the other side of the pipe wall. Assume no loss of energy.   (3 marks)

Show Answers Only

`0.45\ text{metres}

Show Worked Solution

  • No loss of energy so mechanical energy conserved
  • `text{KE}_2 = 0\ text{J}`
  • `g=10\ text{ms}^(-2)`
  • `h_2=2 + h`
`:.\ KE_2 + PE_2` `= KE_1 + PE_1`  
`0 + mgh_2` `= 1/2mv_1^2 + mgh_1`  
`10 xx (2 + h)` `= (1/2 xx 3^2) + (10 xx 2)`  
`20 + 10h` `= 4.5 + 20`  
`h` `= 4.5/10= 0.45\ text{metres}`  

ENGINEERING, AE 2019 HSC 15 MC

Titanium is used to manufacture aircraft undercarriages that support landing wheels.

Why is titanium used in preference to alloy steel for this purpose?

  1. It has lower density and lower strength.
  2. It has lower density and higher strength.
  3. It has higher density and lower strength.
  4. It has higher density and higher strength.
Show Answers Only

`B`

Show Worked Solution
  • Lower density and higher strength, means the material has a very high strength to weight ratio, or specific strength.
  • This is one of the most beneficial characteristics associated with titanium alloys.

`=>B`

ENGINEERING, CS 2019 HSC 9 MC

A sketch of a post-tensioned concrete beam is shown.
 

Which of the following shows the most likely loading condition the beam is designed to resist when viewed from the front?
 

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`D`

Show Worked Solution
  • Concrete has high compressive strength, while the steel reinforcements have high tensile strength.
  • Hence, the most likely loading scenario will put the bottom of the beam in tension and the top in compression. 

`=>D`

ENGINEERING, TE 2019 HSC 2 MC

Which of the following identifies TWO properties of polymers that make them better suited than ceramics for the insulation of telecommunication cables?

  1. Ease of formability and higher density
  2. Ease of formability and higher flexibility
  3. Higher resistance to abrasion and higher density
  4. Higher resistance to abrasion and higher flexibility
Show Answers Only

`B`

Show Worked Solution

By Elimination:

  • Higher density is an undesirable property in cabling (not `A` or `C`)
  • Ceramics have higher resistance to abrasion (not `C` or `D`)

`=>B`

ENGINEERING, TE 2022 HSC 27a

Describe TWO different uses of polymers in telecommunications.   (4 marks)

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Answers could include any two of the following:

Cable protection and insulation

  • Polymers offer protection for both the cable and anyone who may come in contact with it.

Circuit components

  • Polymers are widely used internally in many telecommunication devices.

Device casings and housings

  • Polymers are a common material used for casings for devices such as TV’s and mobile phones.
Show Worked Solution

Answers could include any two of the following:

Cable protection and insulation

  • Polymers offer protection for both the cable and anyone who may come in contact with it.

Circuit components

  • Polymers are widely used internally in many telecommunication devices.

Device casings and housings

  • Polymers are a common material used for casings for devices such as TV’s and mobile phones.

ENGINEERING, PPT 2022 HSC 26b

Different modes of transport emit different amounts of carbon dioxide `(\text{CO}_2)`. For example, petrol cars emit more `\text{CO}_2` than electric cars while in motion.

Describe engineering innovations that have led to lower carbon dioxide emissions from electric transportation.   (3 marks)

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Answers should discuss one of the following:

Electric powered cars

  • Electric powered cars do not need heavy engine components to propel them as their energy comes from an electric source. There are also fewer moving parts resulting in a net decrease in weight.
  • Lighter engineering materials further contribute to the decreased weight, which improves fuel efficiency and lowers `\text{CO}_2` emissions.
  • Furthermore, combustion engines themselves produce large volumes of `\text{CO}_2`, hence their removal greatly decreases emissions.

Electric powered bikes

  • Place lower energy demands on a rider, which decreases the `\text{CO}_2` emissions from the cyclist.
  • Battery technology increases the bike’s range and decreases its emissions, enabling long distance travel without negative environmental impacts.
Show Worked Solution

Answers should discuss one of the following:

Electric powered cars

  • Do not need heavy engine components to propel them as their energy comes from an electric source. There are also fewer moving parts resulting in a net decrease in weight.
  • Lighter engineering materials further contribute to the decreased weight, which improves fuel efficiency and lowers `\text{CO}_2` emissions.
  • Furthermore, combustion engines themselves produce large volumes of `\text{CO}_2`, hence their removal greatly decreases emissions.

Electric powered bikes

  • Place lower energy demands on a rider, which decreases the `\text{CO}_2` emissions from the cyclist.
  • Battery technology increases the bike’s range and decreases its emissions, enabling long distance travel without negative environmental impacts.

ENGINEERING, AE 2022 HSC 25c

Explain how engineers have used their knowledge of both mechanics and hydraulics to contribute to aircraft design. Support your answer with specific examples.   (5 marks)

Show Answers Only
  • Modern aircraft encompass the consolidation of many advancements in mechanical principles and hydraulic systems.
  • Understanding of the mechanics of lift, thrust and drag through the use of wind tunnels and simulations has led to a better understanding of aerodynamics and flight.
  • This led to changes in aircraft design and shape to increase capacity, improve fuel efficiency and decrease drag in the form of wingtip vortices through the introduction of winglets. 
  • An increased understanding of hydraulics has led to improved braking power, allowing for heavier planes to be stopped safely.
  • Coupled with developments in computers, this understanding has also allowed for quick, computer controlled adjustments of control surfaces, with more power and precision than previously possible.
  • Mechanical developments to aircraft propulsion systems have also increased the  fuel efficiency and speed of modern day aircraft.
Show Worked Solution
  • Modern aircraft encompass the consolidation of many advancements in mechanical principles and hydraulic systems.
  • Understanding of the mechanics of lift, thrust and drag through the use of wind tunnels and simulations has led to a better understanding of aerodynamics and flight.
  • This led to changes in aircraft design and shape to increase capacity, improve fuel efficiency and decrease drag in the form of wingtip vortices through the introduction of winglets. 
  • An increased understanding of hydraulics has led to improved braking power, allowing for heavier planes to be stopped safely.
  • Coupled with developments in computers, this understanding has also allowed for quick, computer controlled adjustments of control surfaces, with more power and precision than previously possible.
  • Mechanical developments to aircraft propulsion systems have also increased the  fuel efficiency and speed of modern day aircraft.

ENGINEERING, AE 2022 HSC 24a

An aeronautical engineer is developing a prototype for a new propeller design.

Identify a suitable method of developing the prototype and outline the benefits of using this method.   (3 marks)

Show Answers Only

Possible methods include:

CAD software

  • Prototype can be created and tested using CAD software.
  • This software can quickly produce working models with little difficulty.

3D printing

  • Used alongside CAD, 3D printing allows you to hold a physical model and could allow for simple testing of the design.

CNC Milling

  • Can be used to create a physical prototype out of a variety of materials.
  • Significantly faster than traditional machining of pieces.

Scaled physical model

  • A simple smaller propeller can be used to test ideas and appearances.
Show Worked Solution

Possible methods include:

CAD software

  • Prototype can be created and tested using CAD software.
  • This software can quickly produce working models with little difficulty.

3D printing

  • Used alongside CAD, 3D printing allows you to hold a physical model and could allow for simple testing of the design.

CNC Milling

  • Can be used to create a physical prototype out of a variety of materials.
  • Significantly faster than traditional machining of pieces.

Scaled physical model

  • A simple smaller propeller can be used to test ideas and appearances.

PHYSICS, M8 2015 HSC 34d

In 1927, Davisson and Germer reported the results of an experiment in which they fired electrons at a crystal of nickel and observed how the electrons were scattered.

  1. State their conclusion, with reference to the results they obtained.   (2 marks)
  1. Explain the significance of this experiment to the Rutherford-Bohr model of the atom.   (3 marks)
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i.    Experiment Results:

  • Davisson and Germer found that the electrons were not scattered in a random pattern, but formed an interference pattern after passage through the crystal.
  • This pattern is formed by constructive and destructive wave interference.
  • Conclusion:
  • Since interference is a phenomenon only observed with waves they concluded that electrons were also waves.
     

ii.   The Rutherford-Bohr model:

  • Postulated that electrons existed in fixed orbits. The model however, was unable to explain why only these orbits were stable.
  • The knowledge that electrons are waves provides a plausible explanation for this stability.
  • If electrons act as waves, as indicated by de Broglie, the electron can only exist in orbits where it experiences constructive interference.
Show Worked Solution

i.    Experiment Results:

  • Davisson and Germer found that the electrons were not scattered in a random pattern, but formed an interference pattern after passage through the crystal.
  • This pattern is formed by constructive and destructive wave interference.
  • Conclusion:
  • Since interference is a phenomenon only observed with waves they concluded that electrons were also waves. 

ii.   The Rutherford-Bohr model:

  • Postulated that electrons existed in fixed orbits. The model however, was unable to explain why only these orbits were stable.
  • The knowledge that electrons are waves provides a plausible explanation for this stability.
  • If electrons act as waves, as indicated by de Broglie, the electron can only exist in orbits where it experiences constructive interference.

Mean mark (ii) 54%.

PHYSICS, M8 2015 HSC 34aii

The mass of a polonium-218 nucleus is 218.00897 u, the mass of a lead-214 nucleus is 213.99981 u, and the mass of an alpha particle is 4.00260 u.

Calculate the energy released by this alpha decay.   (3 marks)

Show Answers Only

`9.8 xx10^(-13)\ text{J}`

Show Worked Solution

\(\text{Mass}_{i} = 218.00897\ \text{u} \)

\(\text{Mass}_{f} = 213.99981 + 4.00260 = 218.00241\ \text{u} \)

\(\text{Difference} = 218.00897-218.00241 = 0.00656\ \text{u} \)

\(\text{Difference (kg)} = 0.00656 \times 1.661 \times 10^{-27} = 1.08962 \times 10^{-29}\ \text{kg} \)

`E` `=mc^2`  
  `=1.08962xx10^(-29)xx(3 xx10^8)^2`  
  `=9.8 xx10^(-13)\ text{J}`  

PHYSICS, M8 2015 HSC 33d

The position of the Sun, star `W` and star `Z` are shown on the H-R diagram.
 

The curves `A` and `B` show intensity versus frequency for star `W` and the Sun, measured from the same distance.
 

  1. Identify which curve (`A` or `B`) represents star `W` and justify your choice.   (2 marks)
  1. Account for differences between stars `W` and `Z` that can be deduced from the H-R diagram.   (3 marks)
Show Answers Only

i.    Curve A represents star `W`:

  • `W` is hotter so will emit more energy overall, and peak frequency will be higher.

ii.   Differences displayed in H-R graph:

  • Star `W` lies in the main sequence and is therefore fusing hydrogen to helium, most likely via CNO cycle as it is a large dense star.
  • Star `Z` is past main sequence and is therefore fusing larger elements.
  • Since star `Z` is cooler than `W` (refer to its H-R diagram location ) but has similar luminosity, we can deduce it is much larger than `W`.

Other possible answers could include:

  • Differences in fuel source, size and temperature of the stars.
Show Worked Solution

i.    Curve A represents star `W`:

  • `W` is hotter so will emit more energy overall, and peak frequency will be higher.

ii.   Differences displayed in H-R graph:

  • Star `W` lies in the main sequence and is therefore fusing hydrogen to helium, most likely via CNO cycle as it is a large dense star.
  • Star `Z` is past main sequence and is therefore fusing larger elements.
  • Since star `Z` is cooler than `W` (refer to its H-R diagram location ) but has similar luminosity, we can deduce it is much larger than `W`.

Other possible answers could include:

  • Differences in fuel source, size and temperature of the stars.

PHYSICS, M8 2016 HSC 34bii

Calculate the initial energy level of an electron in a hydrogen atom if it emitted `4.089 × 10^{-19}` J on transition to the `n` = 2 level.   (3 marks)

Show Answers Only

`n_i = 4`

Show Worked Solution

`E/(hc) = 1/lambda`

`E/(hc)` `=R(1/((n_f)^2)-1/((n_i)^2))=R(1/(2^2)-1/((n_i)^2))`  
`1/(n_i)^2` `=1/4-(E)/(Rhc)`  
  `=1/4-(4.089 xx 10^{-19})/(1.097 xx 10^7 xx 6.626 xx 10^(-34) xx 3 xx 10^8)`  
  `=0.06248`  

  
`n_i=sqrt(1/0.06248) = 4`

PHYSICS, M8 2016 HSC 34bi

Outline features of the hydrogen spectrum that Bohr's model could not explain.   (3 marks)

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  • Bohr’s model could not provide an adequate explanation of why some spectral lines were observed to be more intense than others.
  • This result suggested that certain transitions occurred much more frequently than others which Bohr’s model could not explain.
  • With more sensitive instruments, hyperfine lines were discovered to also exist in the spectrum.
  • This indicates there is some splitting of the energy level that Bohr’s model cannot explain.
Show Worked Solution
  • Bohr’s model could not provide an adequate explanation of why some spectral lines were observed to be more intense than others.
  • This result suggested that certain transitions occurred much more frequently than others which Bohr’s model could not explain.
  • With more sensitive instruments, hyperfine lines were discovered to also exist in the spectrum.
  • This indicates there is some splitting of the energy level that Bohr’s model cannot explain.

PHYSICS, M8 2016 HSC 34aii

Explain the stability of `\ _(2)^(4)text{He}` nuclei in terms of TWO forces.   (3 marks)

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Repulsive electrostatic force:

  • The nucleus of the helium atom given contains 2 protons and two neutrons.
  • Protons carry a positive charge so that there is an electrostatic repulsive force that occurs between the protons in the nucleus. 

Attractive strong nuclear force:

  • A strong nuclear force of attraction occurs between proton-proton, neutron-neutron and protons-neutrons.
  • It is a short range force that is strongest when the nucleons are 0.5 to 1.0 the diameter of a proton apart.
  • Inside this range, it is much stronger than the repulsive electrostatic force and is responsible for keeping the nucleus together. 
Show Worked Solution

Repulsive electrostatic force:

  • The nucleus of the helium atom given contains 2 protons and two neutrons.
  • Protons carry a positive charge so that there is an electrostatic repulsive force that occurs between the protons in the nucleus. 

Attractive strong nuclear force:

  • A strong nuclear force of attraction occurs between proton-proton, neutron-neutron and protons-neutrons.
  • It is a short range force that is strongest when the nucleons are 0.5 to 1.0 the diameter of a proton apart.
  • Inside this range, it is much stronger than the repulsive electrostatic force and is responsible for keeping the nucleus together. 

PHYSICS, M8 2017 HSC 34c

The diagrams show features of the hydrogen emission spectrum.
 

With reference to Bohr's postulates, explain how the line at 434.0 nm in the hydrogen emission spectrum is produced. Support your answer with calculations.   (4 marks)

Show Answers Only
  • Bohr’s postulates state that an electron orbits an atom’s nucleus at fixed energy levels.
  • If an electron jumps from a higher energy level to a lower energy level, it will emit a photon that contains an exact amount of energy.
  • The Rydberg equation can be used to calculate a photon’s wavelength.
  • The blue light is part of the visible Balmer series and therefore `n_f=2`.
  • Using `n_f=2`, `lambda` = 434.0 nm: 
`1/lambda` `=R(1/((n_f)^2)-1/((n_i)^2))`  
  `=R(1/(2^2)-1/((n_i)^2))`  
`1/(n_i)^2` `=1/4-1/(lambdaR)`  
`(n_i)^2` `=1/(1/4-1/(1.097 xx 10^7 xx 434 xx 10^9))`  
`n_i` `=5`  
     
  •  The equation shows that a 434 nm wavelength for the emitted photon corresponds to a jump from the 5th energy level to the 2nd energy level.
Show Worked Solution
  • Bohr’s postulates state that an electron orbits an atom’s nucleus at fixed energy levels.
  • If an electron jumps from a higher energy level to a lower energy level, it will emit a photon that contains an exact amount of energy.
  • The Rydberg equation can be used to calculate a photon’s wavelength.
  • The blue light is part of the visible Balmer series and therefore `n_f=2`.
  • Using `n_f=2`, `lambda` = 434.0 nm: 
`1/lambda` `=R(1/((n_f)^2)-1/((n_i)^2))`  
  `=R(1/(2^2)-1/((n_i)^2))`  
`1/(n_i)^2` `=1/4-1/(lambdaR)`  
`(n_i)^2` `=1/(1/4-1/(1.097 xx 10^7 xx 434 xx 10^9))`  
`n_i` `=5`  
     
  •  The equation shows that a 434 nm wavelength for the emitted photon corresponds to a jump from the 5th energy level to the 2nd energy level.

Mean mark 56%.