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BIOLOGY, M6 EQ-Bank 22

The flow chart illustrates the effect of a point mutation on an organism.
 

  1. Outline the series of events from stages 2 to 4 that resulted in the faulty protein.   (3 marks)

  2. Describe how a type of mutagen may have caused the changes observed in stage 2.   (2 marks)

  3. Given the information in the chart shown, describe the effect caused by the mutation in stage 4 and the effect this would have on the organism.   (3 marks)
     
     

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a.    → Stage 2: A mutagen causes a point mutation in the DNA.

→ Stage 3: The mutated DNA transcription into mRNA.

→ Stage 4: The translation of the mRNA into a polypeptide chain which is not functional due to the mutation.

 

b.    Possible causes of Stage 2 observed changes:

→ High frequency photons including gamma and X-rays are regarded as ionising radiation due to their extremely high energy.

→ They can interfere with DNA undergoing replication causing misalignment and a possible substation change.

→ High energy gamma radiation may also cause mutation when directly striking a nitrogenous base.  

 
Answers could also include

→ Chemical mutagens (alkylating, delaminating and structurally similar chemicals).

→ Carcinogenic metals/elements (radon, cadmium)
 

c.   Effects of Stage 4 mutation

→ When considering the above sequence as 2 codons, the chart shows us that this mutation results in an arginine amino becoming a stop codon.

→ This mutation will hence cause a premature termination of the polypeptide and result in a non-functional polypeptide/protein it forms a part of.

→ Due to the severity of this type of mutation it usually results in extensive health complications for affected individuals.

Show Worked Solution

a.    → Stage 2: A mutagen causes a point mutation in the DNA.

→ Stage 3: The mutated DNA transcription into mRNA.

→ Stage 4: The translation of the mRNA into a polypeptide chain which is not functional due to the mutation.

 

b.    Possible causes of Stage 2 observed changes:

→ High frequency photons including gamma and X-rays are regarded as ionising radiation due to their extremely high energy.

→ They can interfere with DNA undergoing replication causing misalignment and a possible substation change.

→ High energy gamma radiation may also cause mutation when directly striking a nitrogenous base.  

 
Answers could also include

→ Chemical mutagens (alkylating, delaminating and structurally similar chemicals).

→ Carcinogenic metals/elements (radon, cadmium)
 

c.   Effects of Stage 4 mutation

→ When considering the above sequence as 2 codons, the chart shows us that this mutation results in an arginine amino becoming a stop codon.

→ This mutation will hence cause a premature termination of the polypeptide and result in a non-functional polypeptide/protein it forms a part of.

→ Due to the severity of this type of mutation it usually results in extensive health complications for affected individuals.

BIOLOGY, M6 EQ-Bank 14 MC

Which of the following is true of a mutation that produces an allele that is dominant?

  1. It would be expected to cause death.
  2. It could give an observable phenotype in a heterozygous genotype.
  3. It could give an observable phenotype only in a homozygous genotype.
  4. It would be expected to spread more quickly through a population than a recessive mutation.
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Show Worked Solution

By Elimination

→ Mutations are not expected to cause death as death is dependant on the location and type of mutation (Eliminate A).

→ A dominant allele mutation vs recessive has no impact on spread in a population (Eliminate D).

→ The change in phenotype is not only possible in homozygous recessive phenotypes but also in heterozygous individuals (Eliminate C).

BIOLOGY, M6 EQ-Bank 6 MC

An evolutionary biologist was investigating the timeframes of genetic divergence between different species of Acacia. She hypothesised that she would get a better indication of the time at which Acacia species diverged by using non-coding DNA segments rather than coding DNA segments.

Why is this hypothesis most likely to be supported by the evidence?

  1. Coding DNA segments never undergo mutation.
  2. Coding DNA segments are less stable over time due to the selection pressures of the environment.
  3. Non-coding DNA segments do not undergo mutation as they are not subject to selection pressures.
  4. Non-coding DNA segments will show greater diversity after divergence as they are not exposed to selection pressures.
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Show Worked Solution

→ Coding DNA cannot vary as much as even point mutations can be harmful or fatal.

→ Non-coding DNA does not impact the individual or their offspring and will therefore show greater variance which can be used as a tool to track species divergence.

BIOLOGY, M5 EQ-Bank 25

A student plans to investigate whether the development of insulin has affected the prevalence of Type 1 diabetes in the human population and subsequently influenced human evolution. She has access to data on Australians with diabetes extending back to 1973 .

  1. Propose a suitable hypothesis for this investigation.   (2 marks)

  2. Identify TWO variables that need to be controlled for this investigation and explain their importance.   (4 marks)

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a.   Two possible hypotheses include:

→ The development of insulin has led to a decrease in the prevalence of Type 1 diabetics.

→ The use of insulin by people who have Type 1 diabetes has increased the prevalence of Type 1 diabetes in the human population.
 

b.  Variables to be controlled

 → The growth of the Australian population in general will statistically lead to a bias in more recent years, where higher a number of individuals with Type 1 diabetes is to be expected.

→ To control this variable, the investigation should be measured using a fixed rate such as ‘per 100 000’.

→ The time of diagnosis and length of time an individual has used insulin can impact the trend of the obtained data.

→ This data must be obtained and accounted for to be able to increase the validity of findings.

Show Worked Solution

a.   Two possible hypotheses include:

→ The development of insulin has led to a decrease in the prevalence of Type 1 diabetics.

→ The use of insulin by people who have Type 1 diabetes has increased the prevalence of Type 1 diabetes in the human population.
 

b.   Variables to be controlled and their importance

 → The growth of the Australian population in general will statistically lead to a bias in more recent years, where higher a number of individuals with Type 1 diabetes is to be expected.

→ To control this variable, the investigation should be measured using a fixed rate such as ‘per 100 000’.

→ The time of diagnosis and length of time an individual has used insulin can impact the trend of the obtained data.

→ This data must be obtained and accounted for to be able to increase the validity of findings.

BIOLOGY, M5 EQ-Bank 26

The diagram shows a model developed in the early 20th century of crossing over of homologous chromosomes.
 

Explain how the difference between this model and our current model of crossing over reflects an increased understanding of the way in which new combinations of genotypes are produced. Support your answer with a diagram.  (4 marks)

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→ The model shows that crossing over occurs between homologous chromosomes before DNA replication. This means that when sister chromatids are formed, they will contain the post-crossing over sequence.

→ In the new model, DNA replication occurs prior to crossing over, where crossing over only occurs when replicated homologous chromosomes line up in tetrads, and only 2 homologous pairs exchange information. 

→ In this way, the new model will produce 4 unique chromatids while the old model will produce only 2. Therefore new model produces a wider range of genetic variability in offspring.

→ Possible unique chromatids:

Show Worked Solution

→ The model shows that crossing over occurs between homologous chromosomes before DNA replication. This means that when sister chromatids are formed, they will contain the post-crossing over sequence.

→ In the new model, DNA replication occurs prior to crossing over, where crossing over only occurs when replicated homologous chromosomes line up in tetrads, and only 2 homologous pairs exchange information. 

→ In this way, the new model will produce 4 unique chromatids while the old model will produce only 2. Therefore new model produces a wider range of genetic variability in offspring.

→ Possible unique chromatids:

BIOLOGY, M5 EQ-Bank 28

  1. Complete the following diagram to show the process by which gametes are formed.   (3 marks)
     

      
  2. How does the segregation of chromosomes during meiosis lead to a wide variety of gametes being produced?   (2 marks)

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“

Show Worked Solution

a.   


 

b.    Process creating wide variety of gametes

→ Independent assortment is the process by which homologous pairs are separated during meiosis into daughter cells.

→ During this process, daughter cell orientation and the cell they are separated into is random and not dependent on any factors.

→ This leads to a great variety in gametes due to the numerous combinations of chromosomes.

BIOLOGY, M5 EQ-Bank 23

Students conducted preliminary experiments to analyse the DNA base composition of five different individuals.

The table shows the experimental data collected.
 

  1. On the grid provided, plot the % Guanine against % Adenine of the individuals analysed and draw a suitable line of best fit.   (3 marks)
     
     

  2. Identify the relationship shown by the data.   (1 mark)

  3. Explain the relationship shown by the data.   (3 marks)

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a.   
       

b.  Relationship: As the % of Adenine increases, the % of Guanine decreases.

c.   Adenine/Guanine relationship

→ Because Adenine pairs with Thymine and Cytosine pairs with Guanine occurring to DNA base pairing rules, each should directly correlate to each other and account for the same % within the DNA composition of any species.

→ There are the only 4 components that make up all DNA composition. This also means that when comparing % of bases that do not pair, such as Adenine and Guanine, they must combine to form 50% of all DNA. This is evident when looking at individuals A and B, as well as C, D and E which are only off by 1-2%, most likely due to human error.

→ This always explains the relationship where an increase in Adenine (and Thymine) % will result in a decrease in Guanine (and Cytosine) % as the A and T pairs now occupy more space in the genome.

Show Worked Solution

a.   
       

b.  Relationship: As the % of Adenine increases, the % of Guanine decreases.

c.   Adenine/Guanine relationship

→ Because Adenine pairs with Thymine and Cytosine pairs with Guanine occurring to DNA base pairing rules, each should directly correlate to each other and account for the same % within the DNA composition of any species.

→ There are the only 4 components that make up all DNA composition. This also means that when comparing % of bases that do not pair, such as Adenine and Guanine, they must combine to form 50% of all DNA. This is evident when looking at individuals A and B, as well as C, D and E which are only off by 1-2%, most likely due to human error.

→ This always explains the relationship where an increase in Adenine (and Thymine) % will result in a decrease in Guanine (and Cytosine) % as the A and T pairs now occupy more space in the genome.

BIOLOGY, M5 EQ-Bank 27

Explain why internal fertilisation is a more robust process than external fertilisation in maintaining a species generation after generation.   (5 marks)

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→ In order for a species to successfully continue and avoid extinction, a sufficient number of offspring must be able to survive until gestational maturity and produce offspring themselves, hence continuing the cycle.

→ External fertilisation is used mainly in sea animals such as fish where the survival rate of offspring is low due to the plentiful numbers of predators in such a vast environment.

→ In response to this environment, external fertilisation methods must produce large numbers of sperm and eggs to increase the number of fertilised embryos. This process requires of a significant amount of energy.

→ Fertilised embryos typically experience minimal or no parental care, further lowering the survival rate of offspring. Therefore, external fertilisation has numerous disadvantages to overcome in achieving the continuity of the species.

→ Internal fertilisation is generally more common amongst varying species (such as humans). Despite often only producing one child at a time, internal fertilisation as a process protects the developing embryo inside the female uterus.

→ Although the number of fertilised embryos is lower, greater parental care throughout most of early life and a significant decrease in predation creates a higher survival rate.

→ In this way, internal fertilisation is more advantageous to ensure the continuity of a species.

Show Worked Solution

→ In order for a species to successfully continue and avoid extinction, a sufficient number of offspring must be able to survive until gestational maturity and produce offspring themselves, hence continuing the cycle.

→ External fertilisation is used mainly in sea animals such as fish where the survival rate of offspring is low due to the plentiful numbers of predators in such a vast environment.

→ In response to this environment, external fertilisation methods must produce large numbers of sperm and eggs to increase the number of fertilised embryos. This process requires of a significant amount of energy.

→ Fertilised embryos typically experience minimal or no parental care, further lowering the survival rate of offspring. Therefore, external fertilisation has numerous disadvantages to overcome in achieving the continuity of the species.

→ Internal fertilisation is generally more common amongst varying species (such as humans). Despite often only producing one child at a time, internal fertilisation as a process protects the developing embryo inside the female uterus.

→ Although the number of fertilised embryos is lower, greater parental care throughout most of early life and a significant decrease in predation creates a higher survival rate.

→ In this way, internal fertilisation is more advantageous to ensure the continuity of a species.

BIOLOGY, M5 EQ-Bank 16 MC

A student conducted a survey to determine the phenotype prevalence of cats that had long hair in comparison to the number that had short hair in a population of cats.

She asked her classmates to describe the coat length of their cats and tallied the results. Out of 26 cats that were counted, she found that 42% of the cats had long hair and 58% had short hair, and that the trait did not follow a Mendelian ratio.

Which of the following best explains why the results did not follow a Mendelian ratio?

  1. The student tallied the numbers incorrectly.
  2. The length of cat hair may be determined by more than one gene.
  3. The student cannot determine the genotype from the phenotype alone.
  4. The students were unclear about whether their cat had long or short hair.
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Show Worked Solution

By Elimination

→ A and D relate to human error and cannot be deemed a valid reason for an experiment not appealing to a hypothesis (Eliminate A and D).

→ Many characteristics (phenotypes) are controlled by a variety of genes, including standard Mendelian alleles, sex-linked genes, multiple alleles and incomplete dominance/co-dominace. A combination of these may relate to the length of hair in cats, and is the best explanation of the results.

BIOLOGY, M5 EQ-Bank 15 MC

It is suspected that a child has a recessive, sex-linked condition. An initial pedigree was developed.

Which of the following is most likely to depict this initial pedigree?
 

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Show Worked Solution

By Elimination

→ Pedigree C displays no information related to the question as no children are affected (Eliminate C).

→ Both pedigree A and D display crosses which are inaccurate and impossible to occur as daughters cannot be affected if the mother does not have recessive sex-linked traits (Eliminate A and D).

BIOLOGY, M5 EQ-Bank 13 MC

Haemophilia A is a blood clotting disorder that arises from a defect in the gene which is carried on the chromosome.

A couple is considering starting a family. However, the father suffers from Haemophilia A. The mother is healthy with no family history of the disease.

What is the probability that a potential grandson will have Haemophilia A if they have a daughter who partners with an unaffected man?

  1. 0%
  2. 50%
  3. 75%
  4. 100%
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Show Worked Solution

→ The probability can be explained by the cross below, where the daughter has a heterozygous phenotype (mother was homozygous recessive and father had haemophilia).

→ Daughter :    Husband :

→ This shows that 1 in 2 grandsons will have haemophilia and 1 in 2 granddaughters will have haemophilia, therefore there is a 50% likelihood of grandchildren being affected.

BIOLOGY, M5 EQ-Bank 12 MC

The table shows the base triplets in mRNA for amino acids.

From the table, the amino acid Tryptophan (Trp) can be coded for by the base triplet .
 

Which base triplet could code for the amino acid Arginine (Arg)?

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Show Worked Solution

→ is the only correct combination for Arginine from options given.

BIOLOGY, M5 EQ-Bank 14 MC

Haemophilia A is a blood clotting disorder that arises from a defect in the gene F8 which is carried on the X chromosome. The disorder affects the production of a glycoprotein that is one of many components needed to form the platelets which form blood clots when a bleed occurs. It is typically treated with infusions of FVIII product, an inactive single chain polypeptide of 2332 amino acids, which is manufactured using DNA technology on human endothelial cells.

Why is the inactive FVIII polypeptide chain used in the treatment of Haemophilia A?

  1. It will prevent bleeds from occurring.
  2. It can take the place of platelets in clotting blood.
  3. It can be used to manufacture the glycoprotein that is affected by the defective F8 gene.
  4. It is used as a gene therapy to help the patient manufacture FVIII in their own endothelial cells.
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Show Worked Solution

→ An inactive single chain polypeptide that has been manufactured by DNA technology from endothelial cells (the single cell layer of blood vessels) would imply that it is the mRNA strand which codes for the glycoprotein.

→ Haemophilia A is a mutation of the F8 which codes for the glycoprotein (or part of it), and therefore injections of this mRNA strand will ‘bypass’ the mutation and allow the body to manufacture the protein itself.

PHYSICS, M8 EQ-Bank 26

Observations and mathematical ideas are critical to the improvement of scientific models.

Discuss this statement with reference to scientific discoveries that have contributed to our understanding of the atom.   (8 marks)

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If scientific models are not consistent with observations and mathematical ideas, then they need to be changed. The historical progression of models of the atom is an example of this scientific method in action.

→ The Geiger-Marsden experiment involved shooting a beam of alpha particles at a thin sheet of gold foil. It was observed that most alpha particles passed through the gold however some bounced back.

→ Rutherford explained these observations in his model. He postulated that a small, dense positively charged nucleus caused the alpha particles to bounce back and that this nucleus was surrounded by orbiting electrons. The atom was mostly empty space so the majority of alpha particles passed through.

→ This model was limited however as an electron orbiting the nucleus would be accelerating and would radiate electromagnetic radiation, losing energy and spiralling into the nucleus.

→ Bohr overcame this limitation and improved the atomic model by analysing observations of the hydrogen spectrum. He postulated that electrons occupied specific energy orbits and could jump from one energy level to another and electrons travelling from a higher to lower energy orbit would emit a photon, corresponding to emission lines on hydrogen’s spectrum. 

→ Bohr developed a mathematical model explaining the specific wavelengths emitted which relies on Rydberg’s equation: .

→ This model was limited as it was only able to explain the hydrogen atom and wasn’t able to explain why electrons were quantised in such a way.

→ De Broglie built upon this model by postulating that electrons behaved as a wave. He stated that electrons behaved as standing waves with an integer number of wavelengths fitting the circumference of an orbit.

→ De Broglie’s contribution was critically supported by his mathematical model for calculating the associated wavelength

→ From these examples, it is clear that our understanding of the atom has been increased following observations and improved mathematical models.
 

Answers could also reference:

→ Thomson’s discovery of the electron.

→ Further contributions from Davisson-Germer as well as Schrodinger and Heisenberg.

Show Worked Solution

If scientific models are not consistent with observations and mathematical ideas, then they need to be changed. The historical progression of models of the atom is an example of this scientific method in action.

→ The Geiger-Marsden experiment involved shooting a beam of alpha particles at a thin sheet of gold foil. It was observed that most alpha particles passed through the gold however some bounced back.

→ Rutherford explained these observations in his model. He postulated that a small, dense positively charged nucleus caused the alpha particles to bounce back and that this nucleus was surrounded by orbiting electrons. The atom was mostly empty space so the majority of alpha particles passed through.

→ This model was limited however as an electron orbiting the nucleus would be accelerating and would radiate electromagnetic radiation, losing energy and spiralling into the nucleus.

→ Bohr overcame this limitation and improved the atomic model by analysing observations of the hydrogen spectrum. He postulated that electrons occupied specific energy orbits and could jump from one energy level to another and electrons travelling from a higher to lower energy orbit would emit a photon, corresponding to emission lines on hydrogen’s spectrum. 

→ Bohr developed a mathematical model explaining the specific wavelengths emitted which relies on Rydberg’s equation: .

→ This model was limited as it was only able to explain the hydrogen atom and wasn’t able to explain why electrons were quantised in such a way.

→ De Broglie built upon this model by postulating that electrons behaved as a wave. He stated that electrons behaved as standing waves with an integer number of wavelengths fitting the circumference of an orbit.

→ De Broglie’s contribution was critically supported by his mathematical model for calculating the associated wavelength

→ From these examples, it is clear that our understanding of the atom has been increased following observations and improved mathematical models.
 

Answers could also reference:

→ Thomson’s discovery of the electron.

→ Further contributions from Davisson-Germer as well as Schrodinger and Heisenberg.

PHYSICS, M8 EQ-Bank 27

Explain how the analysis of quantitative observations contributed to the development of the concept that certain matter and energy are quantised.   (9 marks)

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Experiments such as Millikan’s oil drop experiment and others testing the photoelectric effect have demonstrated that certain quantities of matter and energy are quantised which means they are multiples of some fundamental value.

Millikan’s Oil Drop Experiment

→ Millikan’s oil drop experiment was able to show that charge is quantised. 

→ Millikan levitated oil drops in an electric field by balancing the electric and gravitational forces on them. This allowed him to find the electric force acting on each oil drop, and using the mass of the oil drop he found its charge.

→ Analysing his results, he found that the charge on every oil drop was an integer multiple of . This was determined to be the fundamental charge on an electron.

→ Further, with Thompson’s later discovery of the charge to mass ratio of an electron, its mass could be determined.
 

Photoelectric Effect

→ Photoelectric effect experiments showed the quantum properties of light which seemingly contradicted the view of light as a wave.

→ It was found that there was a minimum frequency (energy) of light that would cause photoemission when it was incident upon a metal plate, and no photoemission occurred with light lower than this frequency, regardless of intensity.

→ As one photon would strike one electron on the metal surface, the electron would receive a discrete amount of energy from that photon determined by its frequency . If a photon didn’t have enough energy, an electron couldn’t be removed.

→ This experimental evidence changed the conceptual understanding of energy within physics and provided a basis for the quantisation of the energy of light.
 

Other quantitative experiments that could be explored include:

→ Bohr’s analysis of emission spectra to demonstrate the existence of quantised energy levels in atoms.

→ Cathode ray experiments showing the particle nature of electrons.

→ Blackbody radiation experiments. 

Show Worked Solution

Experiments such as Millikan’s oil drop experiment and others testing the photoelectric effect have demonstrated that certain quantities of matter and energy are quantised which means they are multiples of some fundamental value.

Millikan’s Oil Drop Experiment

→ Millikan’s oil drop experiment was able to show that charge is quantised. 

→ Millikan levitated oil drops in an electric field by balancing the electric and gravitational forces on them. This allowed him to find the electric force acting on each oil drop, and using the mass of the oil drop he found its charge.

→ Analysing his results, he found that the charge on every oil drop was an integer multiple of . This was determined to be the fundamental charge on an electron.

→ Further, with Thompson’s later discovery of the charge to mass ratio of an electron, its mass could be determined.
 

Photoelectric Effect

→ Photoelectric effect experiments showed the quantum properties of light which seemingly contradicted the view of light as a wave.

→ It was found that there was a minimum frequency (energy) of light that would cause photoemission when it was incident upon a metal plate, and no photoemission occurred with light lower than this frequency, regardless of intensity.

→ As one photon would strike one electron on the metal surface, the electron would receive a discrete amount of energy from that photon determined by its frequency . If a photon didn’t have enough energy, an electron couldn’t be removed.

→ This experimental evidence changed the conceptual understanding of energy within physics and provided a basis for the quantisation of the energy of light.
 

Other quantitative experiments that could be explored include:

→ Bohr’s analysis of emission spectra to demonstrate the existence of quantised energy levels in atoms.

→ Cathode ray experiments showing the particle nature of electrons.

→ Blackbody radiation experiments. 

PHYSICS, M8 EQ-Bank 22

Einstein's equation   is one of the most important equations in the history of physics.

Justify this statement.   (7 marks)

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at its most basic level, expresses the concept that mass and energy are interchangeable.

Its importance is due to its critical role in explaining and analysing a broad range of ideas, processes and phenomena. These include:

→  The energy sourced from the processes of nuclear fission and fusion, including the energy associated with radioactive decay.

→ The relationship between the binding energy of atoms and their mass defect.

→ Mass dilation of objects approaching the speed of light.

→ The fundamental principles and technology upon which nuclear bombs and nuclear reactors operate.

→ Processes which source energy in stars through the conversion of mass into energy.

→ Processes which allow for particle accelerators to operate, allowing us to investigate into the fundamental structure and properties of matter.

Other equations, such as Newton’s Universal Law of Gravity, do not have the same myriad of applications in fields that make up our current understanding of physics.

It is therefore justified in being called one of the most important equations in the history of physics

Show Worked Solution

at its most basic level, expresses the concept that mass and energy are interchangeable.

Its importance is due to its critical role in explaining and analysing a broad range of ideas, processes and phenomena. These include:

→  The energy sourced from the processes of nuclear fission and fusion, including the energy associated with radioactive decay.

→ The relationship between the binding energy of atoms and their mass defect.

→ Mass dilation of objects approaching the speed of light.

→ The fundamental principles and technology upon which nuclear bombs and nuclear reactors operate.

→ Processes which source energy in stars through the conversion of mass into energy.

→ Processes which allow for particle accelerators to operate, allowing us to investigate into the fundamental structure and properties of matter.

Other equations, such as Newton’s Universal Law of Gravity, do not have the same myriad of applications in fields that make up our current understanding of physics.

It is therefore justified in being called one of the most important equations in the history of physics

PHYSICS, M8 EQ-Bank 23

A patient is given an injection containing kg of radioactive technetium-99m which has a half-life of 6 hours.

How much remains undecayed when a scan is taken 3 hours later?   (3 marks)

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Show Worked Solution

Calculating the decay constant:

 
   
   

 
Amount remaining undecayed:

 
   
   
   

PHYSICS, M8 EQ-Bank 17 MC

The graph shown plots isotopes in terms of their numbers of protons and neutrons. When an isotope undergoes nuclear decay, it will move to a different location on the graph. The movement can be represented with an arrow.
 

Which arrow would correctly describe beta negative decay on the graph?
 

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Show Worked Solution

→ In decay, a neutron is converted into a proton and an electron.

→ The number of neutrons decreases by one and the number of protons increase by one.

→ This corresponds to a movement downwards and to the right on the graph.

PHYSICS, M8 EQ-Bank 24

The table shows the quantum numbers of the four lowest states of the hydrogen atom, together with the energies of those states.

Using appropriate calculations, explain a quantum transition that will absorb a photon of wavelength 102 nm?   (3 marks)

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See Worked Solutions

Show Worked Solution

Calculating the energy of the photon:

 
   
   
   

 
→ When a photon with wavelength 102 nm strikes an electron in the ground state of the hydrogen atom, it will transfer its energy to the electron causing it to occupy a shell with greater energy. 

→ The electron absorbing the photon will therefore transition between shells one (ground state) and three, which is approximately the energy difference between these levels as shown in the table.

PHYSICS, M5 EQ-Bank 27

A toy car was placed facing outwards on a rotating turntable. The car was held in place by a force sensor connected to the centre of the turntable. The centre of mass of the car was 0.25 metres from the centre of the turntable. The reading from the force sensor was recorded at varying speeds of rotation. A stopwatch was used to time the rotation of the turntable. The linear velocity was calculated from the period of rotation. The graph shows the force on the car versus the square of the linear velocity of the car.
 


 

  1. Use the graph to determine the mass of the car.   (3 marks)
  1. Identify possible errors in the data and outline how to reduce their effects on the estimation of the mass of the car.   (4 marks)
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a.   0.034 kg

b.   Errors and reduction strategies

→ If the sensor does not produce accurate readings then systemic errors will result. 

→ Inaccurate readings can be minimised by calibrating the sensor. This can be done against a known force such as the force of gravity on a 1 kg mass.

→ If the stopwatch used to time rotations is manually operated, then error due to human inaccuracy and varying reaction times is introduced. Inaccurate calculations of the motion’s period (i.e. timing of one rotation) makes linear velocity estimations () less accurate.

→ A strategy for mitigating this inaccuracy is by using the stopwatch to measure several rotations at a time and then dividing the result by the total number of rotations.

Show Worked Solution

a.   Graph passes through (2,0) and (25, 3.1):

 
   

 
→

→ As the car is undergoing uniform circular motion:

 
 
 
 
   
   

 

b.   Errors and reduction strategies

→ If the sensor does not produce accurate readings then systemic errors will result. 

→ Inaccurate readings can be minimised by calibrating the sensor. This can be done against a known force such as the force of gravity on a 1 kg mass.

→ If the stopwatch used to time rotations is manually operated, then error due to human inaccuracy and varying reaction times is introduced. Inaccurate calculations of the motion’s period (i.e. timing of one rotation) makes linear velocity estimations () less accurate.

→ A strategy for mitigating this inaccuracy is by using the stopwatch to measure several rotations at a time and then dividing the result by the total number of rotations.

PHYSICS, M5 EQ-Bank 26

A baseball is hit with a velocity of 28 m s ¯1 at an angle of 30° to the horizontal at an initial height of 1.0 m above the plate. Ignore air resistance in your calculations.
 

  1. How long does it take the ball to return to the initial height above the ground?   (3 marks)
  1. The ball is hit directly towards a stationary outfielder who is 85 m from the plate. At the instant the ball is hit, the outfielder begins to run towards the plate with constant acceleration.
  2. What is the magnitude of her acceleration if she catches the ball when it is 0.50 m above the ground?  (4 marks)
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Show Worked Solution

a.   At initial height:

Initial vertical velocity: 

Vertical acceleration:

 
 
   
   
 
   

 

b.   At  :

 
   
 
   

 
Using 

 
 
   

 
Horizontal range travelled ():

 
   
   

COMMENT: Note and are in opposite directions and have opposite signs.

  Distance fielder travelled

 
 
 
   

PHYSICS, M5 EQ-Bank 17 MC

Two identical masses are placed at points and . The escape velocity and circular orbital velocity of the mass at point are and . The escape velocity and circular orbital velocity of the mass at point are and . The diagram is drawn to scale and denotes the centre of Earth.
 

The velocity for a body in circular orbit is given by  .

What is the value of ?

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Show Worked Solution

→ The escape velocity of an object is given by

→ As the diagram is to scale, it can be measured that the distance from to is twice that from to .

→ Let  = distance from to   and  = distance from to :

→

→  

→ Hence, →

PHYSICS, M5 EQ-Bank 9 MC

A satellite is orbiting a planet at a fixed altitude.

Which row of the table correctly identifies the magnitude of the work done by the forces on the satellite and the reason for this being the case?

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→ The work done by a force on an object is the product of the displacement of the object and the magnitude of the force in the direction of the displacement.

→ The satellite is orbiting the planet in uniform circular motion, so the force of gravity acts perpendicular to the direction of motion of the satellite.

→ So, zero work is done on the satellite.

Vectors, EXT2 V1 EQ-Bank 11

Point is the circumcentre of triangle which is the centre of the circle that passes through each of its vertices.

Point is the centroid of triangle where the bisectors of each angle within the triangle intersect.

Point is such that .
 

Prove that     (5 marks)

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Calculus, EXT1 C3 EQ-Bank 10

A tank initially contains 300 grams of salt that is dissolved in 50 L of water. A solution containing 15 grams of salt per litre of water is poured into the tank at a rate of 2 litres per minute and the mixture in the tank is kept well stirred.

At the same time, 2 litres of the mixture flows out of the tank per minute.

  1. Find the differential equation, , where represents the mass, in grams, of salt in the tank at time minutes.   (2 marks)

  2. Express in terms of .   (3 marks)

  3. Find the concentration of salt in the liquid in the longer term.   (1 mark)

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i.    


 

ii. 

 
 
   

 

 
 

 

 
   
 
 
 
 

 

iii.  


 

Calculus, EXT1 C3 EQ-Bank 8

A researcher estimates the number of brumbies in a National Park after years can be modelled by the equation

  1. Sketch the function over the first four years of the research.   (2 marks)

  2. Calculate when the brumby population should reach 13 000, giving your answer to 2 decimal places.   (1 mark)

  3. Show that     (2 marks)

  4. What is the maximum growth rate of the brumby population?   (3 marks)

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  1.  
     
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i.   

ii.   

 
 
 
 
 
 
 

 

 iii.   

 
   
   
   
   
   

 

iv. 

 
   
   
   

 

 
 
 
   

 

 

 
   
   

Proof, EXT2 P2 EQ-Bank 2

lines are drawn in a 2-dimensional plane such that no three lines are concurrent and no two lines are parallel.

is the number of regions into which these lines divide the plane with the diagram illustrating that
 

  1. In a similar way, draw diagrams that illustrate and .  (1 mark)

  2. Using the results in part (i), make a conjecture about the general formula for .  (2 marks)

  3. Use mathematical induction to prove the formula from part (ii).  (3 marks)

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i.                              
 
             
 

   


 

ii.   

 
   
   
   
   
   
   

 

 
   
   

 

iii.   


 


 

 
   
   
   
   

 

Calculus, EXT1 C3 EQ-Bank 11

The maximum speed that a hammer can reach after falling vertically from the top of a skyscraper is .

The hammer's  speed, , after falling metres, is given by the differential equation 

  where is a positive constant.

Find an expression of in terms of .    (4 marks)

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Calculus, EXT1 C3 EQ-Bank 9

The rate of fuel running out of a leaking tank can be modelled by the following equation

  where    is the height of the fuel in the tank after hours?

Initially, the height of the fuel in the tank is  4 metres and after 1.5 hours, it has fallen to 3 metres.

At what height of fuel in the tank will it eventually stabilise, giving your answer to the nearest centimetre?  (4 marks)

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Show Worked Solution
 
 
   

 

 
 
 

 

 
 
 
 
 
   
   

 

BIOLOGY, M7 EQ-Bank 24

Scientific advances have resulted in new methods of managing plant diseases and insect pests.

Describe how TWO of these methods have changed the management of plant diseases and/or insect pests.   (5 marks)

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Transgenic Organisms

→ The development transgenic organisms has lead to the creation of GMO’s with ‘built-in’ pesticides. 

→ The modified plant contains a gene from another genus which allows it to be partially or fully resistant to a pest or disease.

→ For example, Bt Cotton is a type of transgenic cotton which has been modified with a gene which makes it almost immune to Bollworm, the number one burden of cotton plant death globally. This means that pesticides for Bollworm do not have to be used, saving time and expense.

Quarantine

→ The knowledge behind the transmission of specific disease has allowed societies to take adequate measures which will have the best chance for reducing the spread of said disease.

→ Quarantine is the process of isolating any imported crops for a certain amount of time dependent on the infection period of a given disease. This significantly reduces the chances of international diseases spreading into Australia.

Show Worked Solution

Transgenic Organisms

→ The development transgenic organisms has lead to the creation of GMO’s with ‘built-in’ pesticides. 

→ The modified plant contains a gene from another genus which allows it to be partially or fully resistant to a pest or disease.

→ For example, Bt Cotton is a type of transgenic cotton which has been modified with a gene which makes it almost immune to Bollworm, the number one burden of cotton plant death globally. This means that pesticides for Bollworm do not have to be used, saving time and expense.

Quarantine

→ The knowledge behind the transmission of specific disease has allowed societies to take adequate measures which will have the best chance for reducing the spread of said disease.

→ Quarantine is the process of isolating any imported crops for a certain amount of time dependent on the infection period of a given disease. This significantly reduces the chances of international diseases spreading into Australia.

BIOLOGY, M6 2014 HSC 33d

The data compare a segment of the eye control gene in mice to the equivalent gene segment in a range of different species. The expression of these genes is necessary for eye development to begin.
 

Note: grey highlighted bases are the same as those in the mouse gene.

  1. With reference to the data in the table, explain why it is possible for different gene sequences to produce the same protein.   (2 marks)

  2. Discuss ONE strength and ONE limitation of using the data shown to determine the evolutionary relationships between these species.   (4 marks)

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i.   Explanation

→ Differences in base sequences can still code for the same amino acid, and therefore the same protein will be produced. This is often referred to as a silent change.

→ A change producing a different amino acid can have no effect on the protein if the amino acids are chemically similar. For example leucine and isoleucine are so similar that a change in DNA sequence resulting in this change will have no effect on the protein it codes for. This is called a neutral change.


♦♦ Mean mark (i) 40%.

ii.   Strengths

→ Despite having different sequences, each polypeptide chain/protein it is a part of will go on to initiate eye development.

→ This provides evidence that a once common ancestor had the eye development gene similar to that of all species, providing evidence of their close ancestry.

→ The average rate of mutation can also be used as a measure of time since divergence from the common ancestor. For example, species 2 may have more recently diverted as it has a genetic similarity of 85% when compared to species 4, which only has 71.66% similarity.
  

Limitations

→ The study only shows the relationship of one gene which is very small in comparison to the whole genome. This is a weak comparison as the rest of the genome may have intense variation and just studying this gene could provide false information.

→ Studying only one gene also increases the risk of encountering back mutations, mutations of a variation which revert back to the original sequence, making the species seem more closely related. This can also give false information about evolutionary relationships and ancestry.


♦♦ Mean mark (ii) 41%.

BIOLOGY, M6 2014 HSC 32e

The text summarises an ethical framework for decision-making related to the use of biotechnologies.

Evaluate the ethics of the use of ONE specific biotechnology in relation to this framework.   (7 marks)

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→ Transgenic organisms are those in which a gene from another species has been inserted into their genome to provide a favourable characteristic to them.

→ The ‘Super Salmon’ is a genetically modified Atlantic salmon which contains genes from the Chinook salmon and Ocean Pout fish which allow it to grow to market size in colder conditions and therefore faster than wild type Atlantic salmon. This has the potential to increase the availability of salmon and therefore providing a benefit to society. However, the transgenic salmon are unnatural and the addition of the gene may effect other parts of the genome, potentially making the salmon unhealthy or harmful for consumption, providing no benefit to society.

→ Roundup-ready soybeans have an implemented gene which allows them to be immune to roundup, a herbicide sprayed onto the crops which kills weeds. While this will increase yield of soybeans as they will be unaffected by roundup, it is toxic to humans and residue could be on the soybeans at sale, providing harm to consumers. The mass use of roundup may also leak and drift into soils, and overtime ecosystems, harming surrounding environments.

→ In the cases above, the adverse effects on society and the environment of both transgenic organisms as stated above should be studied and compared to the positives to decide which has greater influence (Utilitarian Ethics).

→ The companies and groups responsible for development, distribution and sale of the transgenic organisms are also obligated to provide proof that their product does not induce any harm to society or the environment (The Precautionary Principle).

→ Since there is little evidence for short and long term safety of transgenic organisms for the environment and society, a valid case for ethical use of transgenic organisms has not yet been developed. 


♦ Mean mark 55%.

BIOLOGY, M5 2014 HSC 32a

  1. Name the process for the synthesis of a polypeptide chain from a messenger-RNA base sequence.   (1 mark)

  2. Outline the steps in the formation of a functional enzyme from polypeptide chains.   (3 marks)

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i.    Translation


♦ Mean mark (i) 40%.

ii.   Formation of a functional enzyme from polypeptide chains

→ A polypeptide will fold in a certain three-dimensional shape dependent on the amino acids, such as a sheet or a coil.

→ Multiple polypeptide chains will then link together to form a more specific shape. This shape will then go on to do a specific task as a protein.

Note: The following point is old syllabus knowledge.

→ One type of protein is an enzyme, which acts as a biological catalyst on certain substrates, primarily in metabolic reactions. The certain shape an enzyme makes due to the polypeptide chains within it is what dictates which substrate it will act on. 


♦♦ Mean mark (ii) 31%.

BIOLOGY, M8 2014 HSC 31a

The biological structure shown is part of one of the systems in the body.
 

  1. Name the biological structure.   (1 mark)

  2. Outline the steps involved in this system's response to a stimulus.   (3 marks)

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i.   Nerve cell/neuron
  

ii.   Steps involved in system’s response to a stimulus

→ A stimulus is detected by a receptor nerve cell which convert the stimulus to an electrochemical impulse, which is then carried by sensory cells to the brain.

→ The signal reaches a certain segment on the brain depending on what signal was received, where an action is determined to be carried out.

→ Motor neurons carry the signal to an effector, which carries out the response.


♦ Mean mark (ii) 48%.

 

BIOLOGY, M6 2014 HSC 29

Scientists have tried to achieve a viable embryo by fusing two ova (eggs) from the same female.

Explain whether the offspring produced using this process would be a clone of the female whose two ova were used. Use your knowledge of gamete formation and sexual reproduction to support your answer.   (5 marks)

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→ Despite coming from the same female, meiosis and processes within it cause the genetic material within each ova to be different, and thus the offspring will not be a clone.

→ During meiosis, a germ line cell will replicate, split, then split again, resulting in 4 genetically unique daughter gametes.

→ The processes of independent assortment, the random splitting of each chromosome during each stage, as well as crossing over, where like segments of homologous chromosomes can be exchanged creating new combinations, also contribute to the variability amongst daughter cells.

→ When two of these ova (gametes) are fused, the genetic material of each are contributed to the offspring, with some genes being expressed or suppressed depending on the combinations of alleles from each. In this way, the offspring will be genetically different from the female rather than a clone.


♦♦ Mean mark 36%.

BIOLOGY, M7 2014 HSC 18 MC

Two people were exposed to pathogen on the same day. The graph shows the blood antibody levels for that pathogen over the following 28 days for each person.
 

Which of the following best explains these results?

  1. Person 1 had not been previously exposed to pathogen but had a recent organ transplant.
  2. Person 1 had been previously exposed to pathogen .
  3. Person 2 had already been vaccinated against pathogen .
  4. Person 2 had recent contact with a person infected with a similar pathogen.
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By Elimination

→ Being vaccinated against a pathogen or being exposed to a similar pathogen would lead to higher antibody counts, not lower. (Eliminate C and D).

→ Person 1’s previous exposure to the pathogen means that memory B cells can quickly and rapidly differentiate into plasma B cells, leading to higher counts of antibodies in a shorter time. An organ transplant is not relevant in this scenario. (Eliminate A).


♦ Mean mark 50%.

BIOLOGY, M7 2014 HSC 17 MC

When B cells are activated they divide to form a large number of antibody-secreting cells.

How is this best explained?

  1. Mitosis and gene expression produce cytotoxic cells.
  2. Mitosis and differentiation produce B cells that repair tissues.
  3. Mitosis and cell specialisation produce cells that maintain health.
  4. Mitosis and differentiation produce cells for growth and development.
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→ Mitosis allows B cells to divide into identical plasma B cells.

→ Plasma B cells are specialised cells particular to one pathogen, allowing individuals to be protected against it.


♦ Mean mark 56%.

BIOLOGY, M6 2014 HSC 16 MC

What is the best explanation for the successful development of transgenic species?

  1. Artificial pollination works across the plant kingdom.
  2. Nuclear transplantation from cell to cell is easily achieved.
  3. DNA in the biosphere is composed of the same chemical components.
  4. Genes from different animals within the one species are easily combined.
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Show Worked Solution

→ The development of transgenic species is only possible since all nucleotides in all of the worlds’ life is chemically identical.


♦♦ Mean mark 35%.

BIOLOGY, M5 2014 HSC 15 MC

Goltz Syndrome is a condition in humans that adversely affects the skin. It is inherited as a dominant gene carried on the X chromosome.

A man with Goltz Syndrome and a woman who does NOT have the trait have two children, a boy and a girl.

Which of the following is correct about the inheritance of Goltz Syndrome in these children?

  1. Both children have the syndrome.
  2. The girl has the syndrome and the boy does not.
  3. The girl has the syndrome and the boy is a carrier.
  4. The girl has a 50% chance of having the syndrome and the boy has a 0% chance.
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→ A woman with the genotype XgXg will not have Goltz and a male with XGY will have Goltz.

→ A cross between these individuals will mean that all girls will have Goltz as they have to have the XG allele from the father, and no boys will have Goltz, as they have to inherit the Y chromosome from the father, and both X chromosomes from the mother do not have the gene for Goltz.


♦ Mean mark 48%.

BIOLOGY, M7 2014 HSC 12-13 MC

Refer to the following information to answer Questions 12 and 13.

A student conducted a first-hand investigation using nutrient broth, beakers and an S-shaped delivery tube in an attempt to model Pasteur's experiment.

The equipment and data collected are shown.
 

Question 12

The data collected by the student are

  1. quantitative because data were collected for fourteen days.
  2. qualitative because the appearance of the broth is described.
  3. qualitative because this is a model of a past scientific experiment.
  4. quantitative because the results were recorded for two different beakers.

Question 13

The student's results were different from Pasteur's results.

Which of the following provides the best explanation for the difference?

  1. The nutrient broth was different from Pasteur's.
  2. The nutrient broth always goes cloudy as it ages.
  3. The nutrient broth was not boiled thoroughly on Day 1 .
  4. The nutrient broths were both exposed to oxygen from the outside air.
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Question 12

By Elimination

→ Quantitative data is one in which numerical values are obtained for comparison. (Eliminate A and D).

→ The data then must be qualitative as it includes a description of the broth’s appearance.

Question 13

→ The apparatus matches that of Pasteur’s, so the best explanation for flask 2 also going cloudy would be due to not thoroughly boiling the broth before the experiment, and therefore not eliminating any bacteria already present.


♦ Mean mark 53%.

ENGINEERING, TE 2017 HSC 16 MC

Television programs that show high levels of activity often have lower picture quality.

This is because television signals are transmitted using

  1. digital modulation at low compression levels.
  2. digital modulation at high compression levels.
  3. analogue modulation at low compression levels.
  4. analogue modulation at high compression levels.
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→ Modern television signals are transmitted using digital modulation, so the answer must be A or B.

→ The lower picture quality is the result of the TV being unable to decompress the highly compressed signal quickly.


♦♦ Mean mark 39%.

ENGINEERING, CS 2017 HSC 10 MC

Which of the following statements describes Hooke's Law?

  1. Pressure acting on an object varies proportionally with depth.
  2. Pressure acting on an object in a confined fluid is uniform in all directions.
  3. Force induced in an object by stretching it is initially proportional to its extension.
  4. Force acting on an object is equal to the stress divided by the cross-sectional area.
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→ Hooke’s Law states that when an object is extended or stretched in the elastic range the extension is proportional to the force applied.

→ That is, stress is proportional to strain below the elastic limit.


♦ Mean mark 45%.

ENGINEERING, PPT 2017 HSC 8 MC

Which row of the table correctly identifies how the properties of a cold worked metal are changed after annealing?
 

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→ Generally, annealing is the heat treating of a metal to produce a soft (decrease in hardness), stress reduced (decrease in internal residual stress) state.

→ By decreasing the hardness and internal stress, the ductility will increase as well.


♦ Mean mark 49%.

ENGINEERING, TE 2017 HSC 7 MC

Wireless networks operate in two distinct frequency bands: 2.4 GHz and 5 GHz.

Which of the following statements is correct?

  1. 5 GHz waves experience lower attenuation and have a lower bandwidth
  2. 5 GHz waves experience higher attenuation and have a higher bandwidth
  3. 2.4 GHz waves experience lower attenuation and have a higher bandwidth
  4. 2.4 GHz waves experience higher attenuation and have a lower bandwidth
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Show Worked Solution

→ Lower frequencies (2.4GHz) are characterised by lower bandwidth but also good range coverage due to their lower attenuation.

→ Higher frequencies such as 5GHz are subject to higher attenuation especially when they encounter solid objects.


♦♦ Mean mark 38%.

ENGINEERING, PPT 2016 HSC 27b

The table compares the emissions of three transport systems - car, train and aircraft.
 

For each transport system shown in the emissions table, explain how an engineering innovation in that transport system has affected the environment.   (7 marks)

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Innovations in car transport include:

→ Fuel injection, turbo engines, power to weight ratio, tyre variants, engine management systems, ABS breaks, regenerative braking and reduction in drive train losses.

Environmental Impacts

→ Improved power to weight ratios have led to greater fuel efficiency (less consumption).

→ This has resulted from innovations in the strength of aluminium alloys and the use of carbon fibre composite components both of which make the car lighter.

→ Cars with more aerodynamic shapes are also being routinely produced, which reduces drag.

→ Therefore, modern cars that are more aerodynamically designed and built with lighter materials, have considerably less drag, and thus  emissions are reduced.
  

Innovations in rail transport include:

→ Turbo driven diesel engines, magnetic levitation braking, disc brakes, electric trains with AC versus DC motors and efficient track alignment.

Environmental Impacts

→ The use of AC motors in the drive train, rather than DC, has been the most positive modern innovation in rail transport.

→ VVVF (variable voltage variable frequency) drives, control the voltage and torque on modern AC machines, creating greater efficiencies, as DC machines lose electricity as heat.

→ Regenerative braking can be employed by AC machines as a train descends or slows down.

→ These improved efficiencies result in less diesel fuel on country trains and less electricity on city trains, leading to a reduction in  emissions.

  
Innovations in air transport include:

→ The use of composites to create more aerodynamic shapes and reduced weight, improved efficiency in turbofans, reduced drag and the removal of rivet-induced turbulence through the use of adhesives.

Environmental Impacts

→ Fuel efficiency is greatly improved through the use of modern turbofan engines that optimise the entrainment of by bypass air, which produces 90% of the total thrust of the engine.

→ The use of flow control devices and winglets on wings, minimise wing tip vortices, improving lift and reducing drag.

→ Efficiency is therefore improved leading to reduced fuel consumption and a consequent reductions in  emissions.

Show Worked Solution

Innovations in car transport could include:

→ Fuel injection, turbo engines, power to weight ratio, tyre variants, engine management systems, ABS breaks, regenerative braking and reduction in drive train losses.

Environmental Impacts

→ Improved power to weight ratios have led to greater fuel efficiency (less consumption).

→ This has resulted from innovations in the strength of aluminium alloys and the use of carbon fibre composite components both of which make the car lighter.

→ Cars with more aerodynamic shapes are also being routinely produced, which reduces drag.

→ Therefore, modern cars that are more aerodynamically designed and built with lighter materials, have considerably less drag, and thus  emissions are reduced.
  

Innovations in rail transport could include:

→ Turbo driven diesel engines, magnetic levitation braking, disc brakes, electric trains with AC versus DC motors and efficient track alignment.

Environmental Impacts

→ The use of AC motors in the drive train, rather than DC, has been the most positive modern innovation in rail transport.

→ VVVF (variable voltage variable frequency) drives, control the voltage and torque on modern AC machines, creating greater efficiencies, as DC machines lose electricity as heat.

→ Regenerative braking can be employed by AC machines as a train descends or slows down.

→ These improved efficiencies result in less diesel fuel on country trains and less electricity on city trains, leading to a reduction in  emissions.

  
Innovations in air transport could include:

→ The use of composites to create more aerodynamic shapes and reduced weight, improved efficiency in turbofans, reduced drag and the removal of rivet-induced turbulence through the use of adhesives.

Environmental Impacts

→ Fuel efficiency is greatly improved through the use of modern turbofan engines that optimise the entrainment of by bypass air, which produces 90% of the total thrust of the engine.

→ The use of flow control devices and winglets on wings, minimise wing tip vortices, improving lift and reducing drag.

→ Efficiency is therefore improved leading to reduced fuel consumption and a consequent reductions in  emissions.


♦ Mean mark 51%.

ENGINEERING, PPT 2016 HSC 22c

An electrical connector is screwed onto a threaded rod. A flat plate is then secured to the connector by a bolt screwed into a threaded hole.
 

Complete the scaled sectioned front view with the parts assembled.   (6 marks)
 

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The image below should be adjusted to the appropriate scale.

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The image below should be adjusted to the appropriate scale.

Key points for this drawing:

  • Do not dimension unless asked
  • Section lines should be at 45 degrees and 3 mm apart
  • No not section threads/bolts
  • Ensure correct bolts dimensions used for the bolt
  • The gap in the middle shows that the pieces DO NOT sit flush
  • Swap direction of section lines for adjoining areas

♦♦ Mean mark 43%.

ENGINEERING, CS 2016 HSC 21ai

The reinforced concrete modules shown are designed for public seating. A typical use would be as a bus shelter.
 

Outline benefits of using this type of modular seating system.   (3 marks)

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→ Reusable moulds can be used to manufacture the modules off-site and then delivered to the site.

→ The completed modules can then be delivered to the site, resulting in fewer site disruptions.

→ More modules can be added as required.

Show Worked Solution

→ Reusable moulds can be used to manufacture the modules off-site and then delivered to the site.

→ The completed modules can then be delivered to the site, resulting in fewer site disruptions.

→ More modules can be added as required.


Mean mark 54%.

ENGINEERING, PPT 2016 HSC 26c

Structural steel -beams are used to make a crane were hot-rolled then normalised.

Explain why normalising was chosen as the heat treatment process. Support your answer with a labelled sketch of the resulting microstructure.   (4 marks)


 

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Advantages of normalising:

→ An increase in strength. Grain size strengthening is achieved due to the fine uniform grain structure produced by normalising.

→ When compared to other strengthening methods it is relatively economical.

→ Normalising relieves stress.
 

Show Worked Solution

Advantages of normalising:

→ An increase in strength. Grain size strengthening is achieved due to the fine uniform grain structure produced by normalising.

→ When compared to other strengthening methods it is relatively economical.

→ Normalising relieves stress.
 


♦ Mean mark 43%.

ENGINEERING, CS 2016 HSC 26b

What are redundant truss members?   (2 marks)

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Redundant truss members:

→ A truss that carries no load under the conditions present.

→ It is important to note that as load conditions change, the truss may not actually remain redundant. 

Show Worked Solution

Redundant truss members:

→ A truss that carries no load under the conditions present.

→ It is important to note that as load conditions change, the truss may not actually remain redundant. 


♦ Mean mark 46%.

ENGINEERING, CS 2016 HSC 26a

A simplified diagram of a pin jointed truss of a hammerhead crane is shown. It is lifting a load of 54 kN.
 

  1. Calculate the reactions at supports and .   (4 marks)
  1. Determine the magnitude and nature of the force in member .   (2 marks)
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i.     Reaction at = 249 kN ↑

Reaction at = 123 kN @ 12.7° acting down and to the right.

ii.   Force in = 121 kN (Compression)

Show Worked Solution

i.

+  
 
 
   
     
+ ↑  
 
 
   
   

 

Reaction at = 249 kN acting vertically, up

Reaction at = 123 kN @ 12.7° acting down and to the right.
  


Mean mark (i) 52%.

ii.   

   

 
   
   

  
Force in = 121 kN (Compression)


♦ Mean mark (ii) 49%.

ENGINEERING, AE 2016 HSC 25aii

An image of a small drone is shown.
 


  

Nylon propellers are used on drones whereas carbon fibre composite propellers are used on commercial aircraft.

Describe a suitable manufacturing method for each type of propeller.   (3 marks)

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Nylon propellers

→ Injection moulded

→ A screw feeds nylon pellets into a heat chamber.

→ As the screw rotates, a combination of pressure, friction and external heat melts the nylon.

→ Molten nylon is pumped into multi-cavity moulds for setting. 
 

Carbon fibre composite propellers

→ A mould is laid with an impregnated carbon fibre sheet and placed into a vacuum bag.

→ An autoclave is used to evacuate the bag so the assembly can be heated and then allowed to set.

Show Worked Solution

Nylon propellers

→ Injection moulded

→ A screw feeds nylon pellets into a heat chamber.

→ As the screw rotates, a combination of pressure, friction and external heat melts the nylon.

→ Molten nylon is pumped into multi-cavity moulds for setting. 
 

Carbon fibre composite propellers

→ A mould is laid with an impregnated carbon fibre sheet and placed into a vacuum bag.

→ An autoclave is used to evacuate the bag so the assembly can be heated and then allowed to set.


♦♦ Mean mark 36%.