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2013 Notes from the Marking Centre – Engineering Studies

Introduction

This document has been produced for the teachers and candidates of the Stage 6 Engineering Studies course. It contains comments on candidate responses to the 2013 Higher School Certificate examination, highlighting their strengths in particular parts of the examination and indicating where candidates need to improve.

This document should be read along with:

Question 21

Candidates showed strength in these areas:

  • understanding the properties of a specific material that has changed bicycle frames
  • selecting and identifying suitable materials used for early and modern bicycle mudguards and their in-service properties
  • identifying a type of corrosion that could occur at the welded area of the bicycle rack
  • describing how social and environmental issues have influenced the planning of urban infrastructure for bicycles.

Candidates need to improve in these areas:

  • describing how the specific material identified led to a change in bicycle frames
  • contrasting the in-service properties of the chosen materials used for early and modern bicycle mudguards
  • providing the reason why the weld area of the bicycle rack corroded
  • demonstrating an understanding of what urban infrastructure for bicycles encompasses.

Question 22

Candidates showed strength in these areas:

  • identifying grain flow and directional strength as a major advantage of drop forging and demonstrating a good understanding of the manufacturing processes (part a)
  • providing a clear sequence to calculate mechanical advantage, velocity ratio and efficiency (part b)
  • describing the operation of brushless DC motors (part ci)
  • demonstrating an understanding of how the associated change in energy of a moving bicycle is transferred to a battery due to braking (part cii)
  • correctly identifying and using the equation P = VI to determine current, calculate the life of the battery from current and ampere hours and apply it to distance calculation (part ciii).

Candidates need to improve in these areas:

  • providing reasons why the pedal cranks were manufactured by drop-forging in preference to sand casting (part a)
  • relating velocity ratio of the chain/pedal system to the overall solution (part b)
  • comparing the operation of brushless DC motors to brushed DC motors (part ci)
  • identifying appropriate forms of energy in the descriptions of energy transfer (part cii)
  • linking amperage output, time and distance.

Question 23

Candidates showed strength in these areas:

  • using structural analysis to determine the reactions at supports (part a)
  • drawing shear force and bending moment diagrams (part bi)
  • applying the bending stress formula (part bii)
  • recognising that laminated timber beams have improved bending strength properties over solid timber (part c).

Candidates need to improve in these areas:

  • recognising a redundant member (part a)
  • applying a correct method to calculate internal forces in members of a truss (part a)
  • applying the transfer of shear force values and calculations to produce an accurate bending moment diagram (part bi)
  • interpreting data and application of conversion techniques to substitute compatible units into calculations (part bii)
  • outlining the construction and properties of laminated beams and their advantages in structural applications (part c).

Question 24

Candidates showed strength in these areas:

  • calculating a weight-force when given the mass of a body (part a)
  • identifying the connection between changes in air speed and changes in angle of attack and the effect on drag (part b)
  • listing the basic steps in the heat treatment process for age hardening of Duralumin (part c)
  • linking a change in altitude to a change in air pressure in an altimeter (part d).

Candidates need to improve in these areas:

  • identifying forces applicable for different conditions of flight (part a)
  • distinguishing between optimum heat treatment processes and inappropriate processes (part c)
  • using correct terminology specific to certain materials or heat-treatment processes – particularly those related to steels (part c)
  • differentiating between the operation of an air speed indicator and an altimeter and the role of dynamic pressure and static pressure in those instruments (part d).

Question 25

Candidates showed strength in these areas:

  • general knowledge of benefits of digital versus analogue TV signals (part a)
  • knowledge of LED lighting technology (part b)
  • knowledge of principles of geostationary satellites (part c)
  • identifying ‘elements’ of satellite communication systems (part c)
  • identifying the kinetic energy formula (part d).

Candidates need to improve in these areas:

  • knowledge of ‘attenuation’ versus ‘interference’ (part a)
  • understanding the principles of LCD and plasma TV display technologies (part b)
  • knowledge of the difference between ‘signal’ and hardware (part c)
  • conversion of weight to mass and km/h to m/s (part d).

Question 26

Candidates showed strength in these areas:

  • plotting points to create a load-extension graph (part bi)
  • defining key concepts such as stress and strain (part bii).

Candidates need to improve in these areas:

  • sketching a correct pictorial view of a nut to correct scale (part a)
  • understanding standard representation dimensions for threaded objects (part a)
  • drawing a correct load-extension graph (part bi)
  • calculating quantities such as Young’s Modulus with appropriate values and correct units (part bii)
  • explaining how an engineer would use the property they chose to calculate from the load extension data (part bii).

Question 27

Candidates showed strength in these areas:

  • analysing stimulus material to determine components (part a)
  • drawing shape and proportion including chamfer and drill holes (part b)
  • indicating sectional view as requested (not all to AS1100 standard) (part b)
  • using centreline as required (part b).

Candidates need to improve in these areas:

  • explaining in words what 3 x 45º indicates on their drawing (part a)
  • defining 92 PCD (most said it was the distance from the centre of the object to the drilled holes) (part a)
  • distinguishing between full section and half section drawings (part b)
  • applying AS1100 standards (part b)
  • completing details on front view of half-section (part b).
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