An exploded pictorial drawing of a towbar hitch assembly is shown.
- Complete an assembled front sectional view of the towbar hitch assembly.
- Do NOT dimension. (6 marks)
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A towbar hitch and shear pin is shown.
Explain why hot forging would be used to manufacture the shear pin. (3 marks)
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→ Hot forging creates components that exhibit superior strength compared to casting or machining methods.
→ This process enables the production of more intricate geometries while achieving an ideal combination of mechanical properties.
→ These properties include maximum yield strength, increased ductility, and reduced hardness.
→ Hot forging creates components that exhibit superior strength compared to casting or machining methods.
→ This process enables the production of more intricate geometries while achieving an ideal combination of mechanical properties.
→ These properties include maximum yield strength, increased ductility, and reduced hardness.
A drawing of a scale model aircraft flying at constant velocity in level flight is shown.
Assume that the lift acts as a point load only on each wing and is located as shown in the drawing.
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Explain why a fully hardened steel would need to be tempered.
Support your answer with a labelled sketch of the resulting tempered microstructure. (4 marks)
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Exemplar solution 1:
→ Steel in its fully hardened state exhibits extreme brittleness, limiting its practical applications and making it vulnerable to failure.
→ When exposed to abrupt forces or stress concentrations, fully hardened steel can develop cracks or break catastrophically due to its inability to deform.
→ The tempering process plays a vital role in optimising steel’s mechanical properties, creating an essential balance between hardness and toughness.
→ Through careful tempering, the steel’s characteristics can be precisely tuned to match specific operational requirements, ensuring reliable performance across diverse applications.
→ Martensite by hardening:
Exemplar solution 2:
→ The tempering process serves as a crucial follow-up treatment after quenching, specifically designed to mitigate the steel’s brittle characteristics.
→ The procedure involves carefully reheating the hardened steel to a temperature below its critical point, followed by another cooling cycle.
→ This methodical heating and cooling sequence helps release internal stresses that developed during the initial quenching phase.
→ Through tempering, manufacturers can precisely adjust the balance between the steel’s hardness and toughness to achieve desired mechanical properties.
→ Ferrite and finely dispersed cementite:
Exemplar solution 1:
→ Steel in its fully hardened state exhibits extreme brittleness, limiting its practical applications and making it vulnerable to failure.
→ When exposed to abrupt forces or stress concentrations, fully hardened steel can develop cracks or break catastrophically due to its inability to deform.
→ The tempering process plays a vital role in optimising steel’s mechanical properties, creating an essential balance between hardness and toughness.
→ Through careful tempering, the steel’s characteristics can be precisely tuned to match specific operational requirements, ensuring reliable performance across diverse applications.
→ Martensite by hardening:
Exemplar solution 2:
→ The tempering process serves as a crucial follow-up treatment after quenching, specifically designed to mitigate the steel’s brittle characteristics.
→ The procedure involves carefully reheating the hardened steel to a temperature below its critical point, followed by another cooling cycle.
→ This methodical heating and cooling sequence helps release internal stresses that developed during the initial quenching phase.
→ Through tempering, manufacturers can precisely adjust the balance between the steel’s hardness and toughness to achieve desired mechanical properties.
→ Ferrite and finely dispersed cementite:
Brushless DC motors are used to power electric-powered bicycles.
Why are these types of motors so well suited to this application? (3 marks)
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→ Electronic commutation in brushless DC motors enables straightforward control and enhanced operational efficiency.
→ This precise control of speed and torque makes these motors particularly suitable for e-bike applications.
→ Since there are no brushes to wear down, these motors offer improved durability and longevity.
→ Their ability to deliver substantial torque even at lower speeds gives riders the power they need when starting from a stop or tackling inclines.
Answers could also include the following points:
→ Regenerative braking
→ Efficiency
→ Compact size and lightweight.
→ Electronic commutation in brushless DC motors enables straightforward control and enhanced operational efficiency.
→ This precise control of speed and torque makes these motors particularly suitable for e-bike applications.
→ Since there are no brushes to wear down, these motors offer improved durability and longevity.
→ Their ability to deliver substantial torque even at lower speeds gives riders the power they need when starting from a stop or tackling inclines.
Answers could also include the following points:
→ Regenerative braking
→ Efficiency
→ Compact size and lightweight.
How would impact testing be used during the design and development of a motorcycle helmet? (2 marks)
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→ Laboratory crash simulations assess how helmets will perform in real world accidents.
→ These evaluations measure the helmet’s ability to absorb forces, maintain its structure, and meet required safety certifications.
→ Laboratory crash simulations assess how helmets will perform in real world accidents.
→ These evaluations measure the helmet’s ability to absorb forces, maintain its structure, and meet required safety certifications.
Many scientists have performed experiments to explore the interaction of light and matter.
Analyse how evidence from at least THREE such experiments has contributed to our understanding of physics. (8 marks)
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Students could include any of the following experiments:
Young’s Double-Slit Experiment:
→ Young’s 1801 double slit experiment aimed to determine light’s wave-particle nature.
→ He passed coherent light through two slits and observed the pattern on a screen.
→ Instead of Newton’s predicted two bright bands, Young observed alternating bright and dark bands.
→ This interference pattern occurred due to light diffraction and interference, which re wave properties.
→ The experiment provided strong evidence for light behaving as a wave at macroscopic scales.
Planck and the Blackbody Radiation Crisis:
→ Late 19th century scientists studied the relationship between black body radiation’s wavelength and intensity.
→ Experimental observations showed intensity peaked at a specific wavelength, contradicting classical physics predictions.
→ Classical physics led to the “ultraviolet catastrophe,” which violated energy conservation.
→ Planck’s thought experiment resolved this by proposing energy was transferred in discrete packets (quanta) where
→ This revolutionary idea marked a shift from classical physics to quantum theory.
Einstein and the Photoelectric Effect:
→ In 1905, Einstein built upon Plank’s idea of quantised energy to propose that light was made up of quantised photons where
→ Einstein proposition explained why electrons are ejected from metal surfaces only when light exceeds a minimum frequency.
→ Previous to Einstein’s explanation of the photoelectric effect a high intensity of light corresponds to a high energy.
→ Einstein proposed that the KE of the emitted electrons was proportion to the frequency of the light rather than the intensity of the light.
→ This development in the understanding of the interaction of light and matter at the atomic level shifted our understanding of light to a wave-particle duality model.
Cosmic Ray Experiments and the development of the Standard Model:
→ In 1912, Victor Hess discovered cosmic rays through high-altitude balloon experiments, finding that radiation increased with altitude rather than decreased as expected.
→ The study of cosmic rays led to the unexpected discovery of new particles, including the positron and muon, which couldn’t be explained by the known models of matter.
→ These discoveries from cosmic rays helped inspire the development of modern particle accelerators and contributed to the formulation of the quark model in the 1960s.
→ Eventually further studies on these newly discovered particles led to the development of the Standard Model of particle physics, which organises all known elementary particles and their interactions.
Students could include any of the following experiments:
Young’s Double-Slit Experiment:
→ Young’s 1801 double slit experiment aimed to determine light’s wave-particle nature.
→ He passed coherent light through two slits and observed the pattern on a screen.
→ Instead of Newton’s predicted two bright bands, Young observed alternating bright and dark bands.
→ This interference pattern occurred due to light diffraction and interference, which re wave properties.
→ The experiment provided strong evidence for light behaving as a wave at macroscopic scales.
Planck and the Blackbody Radiation Crisis:
→ Late 19th century scientists studied the relationship between black body radiation’s wavelength and intensity.
→ Experimental observations showed intensity peaked at a specific wavelength, contradicting classical physics predictions.
→ Classical physics led to the “ultraviolet catastrophe,” which violated energy conservation.
→ Planck’s thought experiment resolved this by proposing energy was transferred in discrete packets (quanta) where
→ This revolutionary idea marked a shift from classical physics to quantum theory.
Einstein and the Photoelectric Effect:
→ In 1905, Einstein built upon Plank’s idea of quantised energy to propose that light was made up of quantised photons where
→ Einstein proposition explained why electrons are ejected from metal surfaces only when light exceeds a minimum frequency.
→ Previous to Einstein’s explanation of the photoelectric effect a high intensity of light corresponds to a high energy.
→ Einstein proposed that the KE of the emitted electrons was proportion to the frequency of the light rather than the intensity of the light.
→ This development in the understanding of the interaction of light and matter at the atomic level shifted our understanding of light to a wave-particle duality model.
Cosmic Ray Experiments and the development of the Standard Model:
→ In 1912, Victor Hess discovered cosmic rays through high-altitude balloon experiments, finding that radiation increased with altitude rather than decreased as expected.
→ The study of cosmic rays led to the unexpected discovery of new particles, including the positron and muon, which couldn’t be explained by the known models of matter.
→ These discoveries from cosmic rays helped inspire the development of modern particle accelerators and contributed to the formulation of the quark model in the 1960s.
→ Eventually further studies on these newly discovered particles led to the development of the Standard Model of particle physics, which organises all known elementary particles and their interactions.
A geotextile used in the construction of a retaining wall is shown.
Why are geotextiles used in the construction of retaining walls? (3 marks)
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Answers could include three of the following:
→ They facilitate drainage in water-prone areas while simultaneously distributing structural loads more evenly across the soil base.
→ Additionally, these materials create a stable foundation that prevents soil erosion by holding soil particles in place against water movement.
→ Geotextiles enhance soil stability, by preventing mixing of different soil layers and
improving load-bearing capacity.
→ They reinforce the soil mass, by increasing the overall strength and longevity of the retaining wall system.
Answers could include three of the following:
→ They facilitate drainage in water-prone areas while simultaneously distributing structural loads more evenly across the soil base.
→ Additionally, these materials create a stable foundation that prevents soil erosion by holding soil particles in place against water movement.
→ Geotextiles enhance soil stability, by preventing mixing of different soil layers and improving load-bearing capacity.
→ They reinforce the soil mass, by increasing the overall strength and longevity of the retaining wall system.
Why is single-mode cable used for long distance telecommunications rather than other fibre optic cables?
→ Single-mode fibre optic cable only allows one path for light to travel, reducing signal dispersion and allowing for faster, clearer transmission over long distances.
→ This results in a higher transmission rate and bandwidth compared to multi-mode cables which allow multiple light paths.
An
The load is then increased.
Which increase in dimension would provide the most resistance to bending?
→ The most efficient way to increase bending resistance in an
Which property is necessary in the manufacture of a sheet steel car door panel?
→ Ductility is the ability of the steel to be plastically deformed without breaking.
→ This is essential for pressing and stamping sheet metal into the complex curves and shapes required for car door panels.
When producing glass, what molten material is the glass floated on in order to obtain a smooth surface?
→ In the glass manufacturing process, molten glass is poured onto a bed of molten tin.
→ Tin provides an extremely flat and smooth surface due to tin’s high density and surface tension, allowing the glass to float and spread evenly while cooling.
The cross-section of a tapered tube is shown.
What are the pressure readings at both gauge
→ According to Bernoulli’s principle, as the air velocity increases through the tapered section, the pressure must decrease.
→ This results in high pressure at the wide entrance (gauge A) where velocity is low and low pressure at the narrow exit (gauge B) where velocity is high.
A shear force diagram is shown.
Which of the following beams is represented in the shear force diagram?
→ For a simply supported beam with a uniformly distributed load, the shear force diagram shows a linear variation that begins with a positive reaction at the left support and decreases linearly to a negative value at the right support.
→ This linear pattern occurs because the distributed load gradually transfers the shear force from one support to the other, with zero shear at the beam’s midspan where the direction of shear changes.
A magnet is swinging as a pendulum. Close below it is an aluminium (non-ferromagnetic) can. The can is free to spin around a fixed axis as shown.
Analyse the motion and energy transformations of both the can and the magnet. (7 marks)
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→ When the magnet swings down from its high position toward the can, its gravitational potential energy transforms into kinetic energy.
→ As the magnet moves, it creates changing magnetic flux through the aluminium can. This flux change is strongest when there’s the fastest relative motion between the magnet and can.
→ The induced emf is described in the equation
→ This emf creates eddy currents in the can, which produce both heat and a magnetic field. Following Lenz’s law, this magnetic field opposes the magnet’s motion.
→ The magnetic fields from both the magnet and the eddy currents interact, causing the can to initially rotate clockwise.
→ Eventually, this interaction dampens the magnet’s swing. The magnetic interaction between the eddy currents and the magnet causes the can to rotate back and forth with decreasing amplitude, as the system’s energy gradually converts to heat.
→ When the magnet swings down from its high position toward the can, its gravitational potential energy transforms into kinetic energy.
→ As the magnet moves, it creates changing magnetic flux through the aluminium can. This flux change is strongest when there’s the fastest relative motion between the magnet and can.
→ The induced emf is described in the equation
→ This emf creates eddy currents in the can, which produce both heat and a magnetic field. Following Lenz’s law, this magnetic field opposes the magnet’s motion.
→ The magnetic fields from both the magnet and the eddy currents interact, causing the can to initially rotate clockwise.
→ Eventually, this interaction dampens the magnet’s swing. The magnetic interaction between the eddy currents and the magnet causes the can to rotate back and forth with decreasing amplitude, as the system’s energy gradually converts to heat.
In a thought experiment, a projectile is launched vertically from Earth's surface. Its initial velocity is less than the escape velocity.
The behaviour of the projectile can be analysed by using two different models, Model
The effects of Earth's atmosphere and Earth's rotational and orbital motions can be ignored.
Compare the maximum height reached by the projectile, using each model. In your answer, describe the energy changes of the projectile. (4 marks)
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→ Both models start with identical kinetic energy, which completely transforms into gravitational potential energy when the object reaches its highest point.
→ In Model
→ In Model
→ The object in Model
→ Both models start with identical kinetic energy, which completely transforms into gravitational potential energy when the object reaches its highest point.
→ In Model
→ In Model
→ The object in Model
Two horizontal metal rods,
Both rods are then connected to a battery using wires. After the switch is turned on, currents of different magnitude flow in each rod. The rods move to position 2 after time,
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a.
b. Position 2 results from the larger current in rod
→ While rod
→ Following Newton’s third law, the electromagnetic force that rod
→ The magnitude of the electromagnetic force between the rods can be calculated using the formula:
→ Rod
→ Since the greater acceleration of Rod
→ Since Rod
b. Position 2 results from the larger current in rod
→ While rod
→ Following Newton’s third law, the electromagnetic force that rod
→ The magnitude of the electromagnetic force between the rods can be calculated using the formula:
→ Rod
→ Since the greater acceleration of Rod
→ Since Rod
An electron gun fires a beam of electrons at 2.0 × 10
There is a uniform electric field between the plates of 1.5 × 10
Ignore gravitational effects on the electron beam.
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a.
b.
c.
a.
b.
c.
The simplified model below shows the reactants and products of a proton-antiproton reaction which produces three particles called pions, each having a different charge.
There are no other products in this process, which involves only the rearrangement of quarks. No electromagnetic radiation is produced. Assume that the initial kinetic energy of the proton and antiproton is negligible.
Protons consist of two up quarks
The following tables provide information about hadrons and quarks.
Table 1: Hadron Information
Table 2: Quark charges
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a.
b.
c. Problem with prediction:
→ The calculation shows the pions moving faster than light speed (3 × 10
Resolving the problem:
→ Since these pions are moving at extremely high speeds, we need to account for relativity.
→ Relativity means that pions’ mass actually increases as they get faster, which prevents them from ever reaching light speed.
→ Part of the energy given to the pions goes into increasing their mass rather than just increasing their velocity.
a.
b.
c. Problem with prediction:
→ The calculation shows the pions moving faster than light speed (3 × 10
Resolving the problem:
→ Since these pions are moving at extremely high speeds, we need to account for relativity.
→ Relativity means that pions’ mass actually increases as they get faster, which prevents them from ever reaching light speed.
→ Part of the energy given to the pions goes into increasing their mass rather than just increasing their velocity.
Let
Let the point
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a.
b.
c.
d.
a.
b.
c. | |||
d. | ||
Part of the graph of
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The function
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a.
b.
ci.
cii.
a.
b. | ||
ci.
cii. | ||
Let
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a.
b.
a. | ||
b. | ||
Let
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The points shown on the chart below represent monthly online sales in Australia.
The variable
The variable
The graph of
It has a local minimum at (2,2500) and a local maximum at (11,4400).
i. Find, correct to two decimal places, the values of
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ii. Let
Find the values of
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Part of the graph of
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Find the value of
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A model for the temperature in a room, in degrees Celsius, is given by
where
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The amount of energy used by the heater, in kilowatt hours, can be estimated by evaluating the area between the graph of
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Muons are unstable particles produced when cosmic rays strike atoms high in the atmosphere. The muons travel downward, perpendicular to Earth's surface, at almost the speed of light.
Classical physics predicts that these muons will decay before they have time to reach Earth's surface.
Explain qualitatively why these muons can reach Earth's surface, regardless of whether their motion is considered from either the muon's frame of reference or the Earth's frame of reference. (3 marks)
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→ The muon’s are able to reach the Earth’s surface due to Einstein’s special theory of relativity in relation to length contraction and time dilation.
Muon’s frame of reference:
→ The distance to the Earth’s surface is contracted according to
→ Since the muons have to travel a shorter distance than the proper length, they will have time to reach the Earth’s surface before they decay.
Earth’s frame of reference:
→ The time that it takes the muon to decay will be dilated according to
→ Therefore, the muons have a longer half-life and lifespan than predicted by classical physics and will be able to reach the Earth’s surface before they decay.
→ In this way, muons can reach the surface of the Earth from either frame of reference.
→ The muon’s are able to reach the Earth’s surface due to Einstein’s special theory of relativity in relation to length contraction and time dilation.
Muon’s frame of reference:
→ The distance to the Earth’s surface is contracted according to
→ Since the muons have to travel a shorter distance than the proper length, they will have time to reach the Earth’s surface before they decay.
Earth’s frame of reference:
→ The time that it takes the muon to decay will be dilated according to
→ Therefore, the muons have a longer half-life and lifespan than predicted by classical physics and will be able to reach the Earth’s surface before they decay.
→ In this way, muons can reach the surface of the Earth from either frame of reference.
Consider the function
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ii. exactly four
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ii. Find the coordinates of the local maximum of
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iii. Find the values of
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iv. Consider the two tangent lines to the graph of
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Let
i. Using translations only, describe a sequence of transformations of
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ii. Using a dilation and translations, describe a different sequence of transformations of
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The function
An absorption spectrum resulting from the passage of visible light from a star's surface through its hydrogen atmosphere is shown. Absorption lines are labelled
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a.
b.
c. An absorption spectra is produced when:
→ A continuous spectrum of light from a black body such as a star passes through cooler and lower density gas in the outer atmosphere of the star.
→ As the light passes through the gas, electrons in the atoms that make up the cooler gas clouds absorb distinct wavelengths/energy levels of light equal to the difference in energy levels between the electron shells where
→ As the electrons in the atoms fall back into their ground state, they emit the photon of light that they absorb and the photon is then scattered out of the continuous spectrum.
→ The light that remains is then passed through a prism to separate the wavelengths and record the intensities. The black or darkened lines in the absorption spectra is the result of the scattered wavelengths of light.
a. Determined temperature using the peak wavelength:
b. | ||
c. Absorption spectra:
→ Produced when a continuous spectrum of light from a black body such as a star passes through cooler and lower density gas in the outer atmosphere of the star.
→ As the light passes through the gas, electrons in the atoms that make up the cooler gas clouds absorb distinct wavelengths/energy levels of light equal to the difference in energy levels between the electron shells where
→ As the electrons in the atoms fall back into their ground state, they emit the photon of light that they absorb and the photon is then scattered out of the continuous spectrum.
→ The light that remains is then passed through a prism to separate the wavelengths and record the intensities. The black or darkened lines in the absorption spectra is the result of the scattered wavelengths of light.
Development of models of the atom has resulted from both experimental investigations and hypotheses based on theoretical considerations.
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a.i. Role of paraffin wax:
→ Paraffin wax is a rich source of protons.
→ When the paraffin was placed in front of the unknown radiation, the transfer of momentum from the radiation caused protons to be emitted from the paraffin wax.
→ The emitted protons could then be detected and analysed.
→ From studying the protons ejected from the paraffin wax, Chadwick proposed the existence of the neutron.
a.ii. Changes to the model of the atom:
→ Previous to Chadwick’s experiment, the model of the atom proposed by Rutherford consisted of a dense positive charge in the nucleus which was orbited by electrons.
→ In this model however, the protons did not account for the total mass of the nucleus.
→ Through using the conservation of momentum and energy in his experiment, Chadwick proposed the existence of the neutron particle which was slightly heavier than the proton.
→ The model of the atom was updated to include both protons and neutrons in the nucleus which then fully accounted for the mass of the nucleus.
b. Limitations in the Bohr-Rutherford model:
→ Rutherford’s model of the atom stated that electrons orbited the nucleus and were electrostatically attracted to the positive nucleus. This meant that the electrons were in circular motion and were constantly under centripetal acceleration.
→ However, Maxwell predicted that an accelerating charge would emit electro-magnetic radiation and in Rutherford’s model, all atoms should have been unstable as the electrons would emit EMR, lose energy and spiral into the nucleus.
→ Bohr proposed that electrons orbited the nucleus in stationary states at fixed energies with no intermediate states possible where they would not emit EMR but provided no theoretical explanation for this.
De Broglie’s hypothesis:
→ De Broglie proposed that electrons could exhibit a wave nature and could act as matter-waves. The electrons would form standing waves around the nucleus and would no longer be an accelerating particle which addressed the limitation of all atoms being unstable.
→ Further, De Broglie proposed that the standing waves would occur at integer wavelengths where the circumference of the electron orbit would be equal to an integer electron wavelength,
a.i. Role of paraffin wax:
→ Paraffin wax is a rich source of protons.
→ When the paraffin was placed in front of the unknown radiation, the transfer of momentum from the radiation caused protons to be emitted from the paraffin wax.
→ The emitted protons could then be detected and analysed.
→ From studying the protons ejected from the paraffin wax, Chadwick proposed the existence of the neutron.
a.ii. Changes to the model of the atom:
→ Previous to Chadwick’s experiment, the model of the atom proposed by Rutherford consisted of a dense positive charge in the nucleus which was orbited by electrons.
→ In this model however, the protons did not account for the total mass of the nucleus.
→ Through using the conservation of momentum and energy in his experiment, Chadwick proposed the existence of the neutron particle which was slightly heavier than the proton.
→ The model of the atom was updated to include both protons and neutrons in the nucleus which then fully accounted for the mass of the nucleus.
b. Limitations in the Bohr-Rutherford model:
→ Rutherford’s model of the atom stated that electrons orbited the nucleus and were electrostatically attracted to the positive nucleus. This meant that the electrons were in circular motion and were constantly under centripetal acceleration.
→ However, Maxwell predicted that an accelerating charge would emit electro-magnetic radiation and in Rutherford’s model, all atoms should have been unstable as the electrons would emit EMR, lose energy and spiral into the nucleus.
→ Bohr proposed that electrons orbited the nucleus in stationary states at fixed energies with no intermediate states possible where they would not emit EMR but provided no theoretical explanation for this.
De Broglie’s hypothesis:
→ De Broglie proposed that electrons could exhibit a wave nature and could act as matter-waves. The electrons would form standing waves around the nucleus and would no longer be an accelerating particle which addressed the limitation of all atoms being unstable.
→ Further, De Broglie proposed that the standing waves would occur at integer wavelengths where the circumference of the electron orbit would be equal to an integer electron wavelength,
The function
The function
Twelve students sit in a classroom, with seven students in the first row and the other five students in the second row. Three students are chosen randomly from the class.
The probability that exactly two of the three students chosen are in the first row is
Suppose a function
Consider the function
The inverse of
The following graph, based on the data gathered by Hubble, shows the relationship between the recessional velocity of galaxies and their distance from Earth.
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a. Recessional velocity vs distance from Earth graph:
→ The graph shows that the further away galaxies are from Earth, the faster these galaxies are moving away from Earth.
→ This relationships depicts Hubble’s law:
→ This graph provides evidence that the universe is constantly expanding as predicted by the big bang theory.
b. Determining recessional velocities:
→ The recessional velocities of the galaxies were determined by analysing their absorption spectras.
→ Light waves that are moving away from the Earth will appear to be stretched (wavelength increased) according to the doppler effect.
→ The absorption spectra of galaxies were compared with the spectra of the same elements on Earth, revealing that the galaxies’ spectra were redshifted.
→ The greater the extent of the red shift in the spectra, the greater the recessional velocity of the galaxy.
a. Recessional velocity vs distance from Earth graph:
→ The graph shows that the further away galaxies are from Earth, the faster these galaxies are moving away from Earth.
→ This relationships depicts Hubble’s law:
→ This graph provides evidence that the universe is constantly expanding as predicted by the big bang theory.
b. Determining recessional velocities:
→ The recessional velocities of the galaxies were determined by analysing their absorption spectras.
→ Light waves that are moving away from the Earth will appear to be stretched (wavelength increased) according to the doppler effect.
→ The absorption spectra of galaxies were compared with the spectra of the same elements on Earth, revealing that the galaxies’ spectra were redshifted.
→ The greater the extent of the red shift in the spectra, the greater the recessional velocity of the galaxy.
The diagram shows a type of particle accelerator called a cyclotron.
Cyclotrons accelerate charged particles, following the path as shown.
An electric field acts on a charged particle as it moves through the gap between the dees. A strong magnetic field is also in place.
Once a charged particle has the required velocity, it exits the accelerator towards a target.
Which of the following is true about a charged particle in a cyclotron?
→ When the charged particle is between the dees, it will experience an acceleration due to the electric field present where
→ When the charged particle is inside of the dees, the particle undergoes uniform circular motion due to the strong magnetic field in place from the electromagnets.
→ While the magnitude of the velocity of the charged particle does not change, the direction of the velocity does. Hence, there is a change in velocity of the particle so it is experiencing an acceleration.
→ A charged particle will experience a centripetal force/acceleration when moving perpendicular to a magnetic field.
The graph shows the relationship between the maximum kinetic energy of emitted photoelectrons and the incident photon energy for four different metal surfaces.
Light of frequency
From which metals are photoelectrons emitted?
→ The photon energy for a light frequency of
→ The energy of the light frequency in electron volts
→ Photoelectrons will only be emitted if the energy of the incident photons is enough to overcome the work function of the metals. On the graph above, the work function of each metal is the same value as the x-intercepts of their respective graphs.
→ Therefore photoelectrons will be emitted from potassium and lithium as the energy of the incident photons
A uniform magnetic field is directed into the page. A conductor
Which graph shows the emf induced between the ends of the conductor,
→ As the conductor rotates in the magnetic field, all of the charges in the conductor will have a velocity.
→ This will produce a force on each positive and negative charge in the rod according to the equation
→ Using the right hand rule, the direction of the force applied to each positive charge in the rod during the rotation will be towards
→ This separation of positive and negative charges to opposite ends of the conductor generates the emf.
→ As the velocity of the charges during the circular motion will remain constant, the force on the charges will be constant. Therefore, a constant emf will be produced in the conductor.
The velocity of a proton
What is the de Broglie wavelength of the alpha particle?
→ Let the mass of the proton be
→ Therefore the mass of the alpha particle will be
→ The de Broglie wavelength of the proton,
→ Hence the de Broglie wavelngth of the alpha particle
A rod carrying a current,
How many degrees must the rod be rotated clockwise so that it experiences a force
→ The force experienced by a current carrying conductor in a magnetic field is given by
→ For the rod to experience a force of
→ As the angle between the current carrying conductor and magnetic field lines originally is
A pure sample of polonium-210 undergoes alpha emission to produce the stable isotope lead-206.
The half-life of polonium-210 is 138 days.
At the end of 276 days, what is the ratio of polonium-210 atoms to lead-206 atoms in the sample?
→ After two half-life’s of the polonium only one quarter of the sample of polonium-210 atoms will be left.
→ Therefore, three quarters of the polonium-210 atoms would have decayed into lead-206 atoms.
→ The ratio of polonium atoms to lead atoms is
Which of the following is a fundamental particle in the Standard Model of matter?
→ Hadrons are subatomic particles which are composed of two or more quarks. Protons and Neutrons are categorised as hadrons as they are both composed of 3 quarks.
→ Hadrons, protons and neutrons are not fundamental particles as they are all composed of quarks.
→ The photon is a fundamental particle, classified as a gauge boson and mediates the electromagnetic force.
The graph shows the results of a survey conducted to determine if children changed their method of communication after cochlear implantation.
With reference to the data, describe how cochlear implants work, and how they affect communication in children. (5 marks)
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→ Cochlear implants are surgical electronic devices that help restore hearing in patients with cochlear damage.
→ The implants are inserted directly into the cochlea and stimulate the auditory nerve by sending sound signals straight to the brain.
→ The graph demonstrates that the age of implantation significantly affects communication outcomes.
→ Early implantation (under 3 years): Dramatic decrease in sign language use, with only 10% (approximately) still signing after 5 years.
→ Middle age implantation (3-5 years): Moderate decrease in sign language use.
→ Late implantation (over 5 years): Little to no change in sign language use
→ The data clearly shows that earlier cochlear implantation leads to greater shifts away from sign language as the primary mode of communication.
→ Cochlear implants are surgical electronic devices that help restore hearing in patients with cochlear damage.
→ The implants are inserted directly into the cochlea and stimulate the auditory nerve by sending sound signals straight to the brain.
→ The graph demonstrates that the age of implantation significantly affects communication outcomes.
→ Early implantation (under 3 years): Dramatic decrease in sign language use, with only 10% (approximately) still signing after 5 years.
→ Middle age implantation (3-5 years): Moderate decrease in sign language use.
→ Late implantation (over 5 years): Little to no change in sign language use
→ The data clearly shows that earlier cochlear implantation leads to greater shifts away from sign language as the primary mode of communication.
Discuss the ethical implications and impacts on society of the use of TWO biotechnologies. (7 marks)
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Social impacts of recombinant DNA technology (plant biotechnology)
→ Recombinant DNA has created beneficial products like Bt corn and Bt cotton.
→ Bt crops require fewer pesticide applications since they produce their own insecticidal proteins.
→ This reduces chemical pesticide costs for farmers and decreases environmental impact from pesticide spraying.
Associated ethical concerns:
→ Farmers growing Bt corn and cotton must purchase, at a significant cost, new GM seeds each season. Traditional farmers can reuse their seeds for the following year’s crop planting.
→ This difference creates economic disparities in access to GM crops and the related market opportunities.
Social impacts of selective breeding/hybridisation (animal biotechnology)
→ Selective breeding/hybridisation has produced, for example, dairy cows capable of increased milk production.
→ This results in higher yields and greater food availability.
→ Improved profits and living standards for farmers who can access the technology.
→ Increased food production to support population growth.
Associated ethical issues:
→ High-yield dairy cows show decreased fertility.
→ May compromise animal welfare and quality of life.
Social impacts of recombinant DNA technology (plant biotechnology)
→ Recombinant DNA has created beneficial products like Bt corn and Bt cotton.
→ Bt crops require fewer pesticide applications since they produce their own insecticidal proteins.
→ This reduces chemical pesticide costs for farmers and decreases environmental impact from pesticide spraying.
Associated ethical concerns:
→ Farmers growing Bt corn and cotton must purchase, at a significant cost, new GM seeds each season. Traditional farmers can reuse their seeds for the following year’s crop planting.
→ This difference creates economic disparities in access to GM crops and the related market opportunities.
Social impacts of selective breeding/hybridisation (animal biotechnology)
→ Selective breeding/hybridisation has produced, for example, dairy cows capable of increased milk production.
→ This results in higher yields and greater food availability.
→ Improved profits and living standards for farmers who can access the technology.
→ Increased food production to support population growth.
Associated ethical issues:
→ High-yield dairy cows show decreased fertility.
→ May compromise animal welfare and quality of life.
Female Jack Jumper ants (Myrmecia pilosula) have a single pair of chromosomes. During meiosis, crossing over occurs. The diagram shows the crossing over and the position of three genes on the chromosomes.
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a. Significance of crossing over:
→ Genetic variation increases in the Jack Jumper ant population through recombination.
→ This enhanced genetic diversity improves the species’ chances of survival when faced with environmental changes, as some ants may carry beneficial adaptations.
b.
a. Significance of crossing over:
→ Genetic variation increases in the Jack Jumper ant population through recombination.
→ This enhanced genetic diversity improves the species’ chances of survival when faced with environmental changes, as some ants may carry beneficial adaptations.
b.
Helicobacter pylori is a bacterium that invades the gut lining and can cause damage to the stomach as shown in the diagram.
With reference to innate and adaptive immunity, explain how the body responds after exposure to Helicobacter pylori. (7 marks)
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→ Damaged cells release chemicals that trigger inflammation as an initial response.
→ The inflammatory response causes blood vessels to dilate, increasing blood flow and allowing phagocytes (macrophages and neutrophils) to move into the infected area.
→ Phagocytes process H.pylori antigens and present them to helper T-cells, which launch the adaptive immune response by releasing cytokines.
→ This cytokine release activates both T and B cells to mount multiple specific defences.
→ Cytotoxic T-cells directly attack H.pylori while memory T-cells remain for secondary rapid responses.
→ Suppressor T-cells regulate the immune response and plasma B-cells produce H.pylori-specific antibodies. Memory B-cells persist for responding to future (secondary) infections.
→ Antibodies work in two ways – direct neutralisation of antigens and tagging antigens for destruction by phagocytes.
The immune response involves both innate and adaptive immunity systems working together:
→ Innate immunity provides rapid, immediate defence.
→ Adaptive immunity develops more slowly but offers long-term protection through memory cells.
→ Damaged cells release chemicals that trigger inflammation as an initial response.
→ The inflammatory response causes blood vessels to dilate, increasing blood flow and allowing phagocytes (macrophages and neutrophils) to move into the infected area.
→ Phagocytes process H.pylori antigens and present them to helper T-cells, which launch the adaptive immune response by releasing cytokines.
→ This cytokine release activates both T and B cells to mount multiple specific defences.
→ Cytotoxic T-cells directly attack H.pylori while memory T-cells remain for secondary rapid responses.
→ Suppressor T-cells regulate the immune response and plasma B-cells produce H.pylori-specific antibodies. Memory B-cells persist for responding to future (secondary) infections.
→ Antibodies work in two ways – direct neutralisation of antigens and tagging antigens for destruction by phagocytes.
The immune response involves both innate and adaptive immunity systems working together:
→ Innate immunity provides rapid, immediate defence.
→ Adaptive immunity develops more slowly but offers long-term protection through memory cells.
An epidemiological study was conducted to help model how many people will be affected by Type 2 diabetes globally in the future. Continuous data were collected from 1990 to 2020. From that data, the following data points were chosen to demonstrate the trend.
A prediction of the global population numbers suggests there will be about 9 billion
Predict the number of people that will be affected by diabetes in 2040. Show working on your graph on the previous page and your calculations. (3 marks)
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a.
b. 630 000 000 (630 million)
a.
b. Using the LOBF on the graph:
Population (%) with diabetes in 2040 = 7%
People with diabetes in 2040 =
A study monitored the changes in the body temperature of a kookaburra (an Australian bird) and a human over a 24-hour period. The results of the study are shown in the graph.
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Some endothermic organisms can display torpor (a significant decrease in physiological activity).
With reference to the graph, explain whether the human or the kookaburra was displaying torpor and if so, state the time this occurred. (3 marks)
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a. 4 am
b. Signs of torpor:
→ The human maintained a steady body temperature throughout the observed period, showing no signs of torpor or reduced physiological activity
→ In contrast, the kookaburra exhibited classic torpor behaviour.
→ Its body temperature dropped significantly between 5 pm and 4 am, demonstrating the characteristic reduction in physiological functions during this period.
c. Kookaburra adaptation:
→ Kookaburras have an effective insulation mechanism where they puff out their feathers, creating space between them.
→ This fluffing action traps a layer of warm air between the feathers and the bird’s body, forming an insulating barrier
→ The trapped air pocket acts like natural insulation, minimising heat loss and helping the kookaburra maintain its body temperature efficiently.
a. 4 am
b. Signs of torpor:
→ The human maintained a steady body temperature throughout the observed period, showing no signs of torpor or reduced physiological activity
→ In contrast, the kookaburra exhibited classic torpor behaviour.
→ Its body temperature dropped significantly between 5 pm and 4 am, demonstrating the characteristic reduction in physiological functions during this period.
c. Kookaburra adaptation:
→ Kookaburras have an effective insulation mechanism where they puff out their feathers, creating space between them.
→ This fluffing action traps a layer of warm air between the feathers and the bird’s body, forming an insulating barrier
→ The trapped air pocket acts like natural insulation, minimising heat loss and helping the kookaburra maintain its body temperature efficiently.
The diagram shows a simplified version of the process of polypeptide synthesis.
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a. Process
→ Both DNA replication and transcription (Process
→ DNA replication’s goal is to create two identical DNA molecules, with each containing one original and one new strand.
→ In contrast, transcription copies just one DNA strand to produce a single mRNA strand.
b. mRNA and tRNA’s role in polypeptide synthesis:
→ mRNA is created in the nucleus by copying a DNA template during transcription.
→ This mRNA molecule serves as a messenger, carrying genetic instructions (in the form of codons) from the nucleus out to ribosomes in the cytoplasm.
→ At the ribosome, translation kicks in – this is where the genetic code gets converted into protein.
→ tRNA molecules are key players here – each has an anticodon that matches up with specific codons on the mRNA strand.
→ The process flows like an assembly line: mRNA codons are read in sequence, tRNA molecules bring in matching amino acids, and these amino acids are linked together to form a polypeptide chain.
a. Process
→ Both DNA replication and transcription (Process
→ DNA replication’s goal is to create two identical DNA molecules, with each containing one original and one new strand.
→ In contrast, transcription copies just one DNA strand to produce a single mRNA strand.
b. mRNA and tRNA’s role in polypeptide synthesis:
→ mRNA is created in the nucleus by copying a DNA template during transcription.
→ This mRNA molecule serves as a messenger, carrying genetic instructions (in the form of codons) from the nucleus out to ribosomes in the cytoplasm.
→ At the ribosome, translation kicks in – this is where the genetic code gets converted into protein.
→ tRNA molecules are key players here – each has an anticodon that matches up with specific codons on the mRNA strand.
→ The process flows like an assembly line: mRNA codons are read in sequence, tRNA molecules bring in matching amino acids, and these amino acids are linked together to form a polypeptide chain.
Cystic fibrosis is an inherited disorder that causes damage to the lungs, digestive system and other organs in the body. A person with cystic fibrosis will have two faulty recessive alleles for the cystic fibrosis gene (CFTR) on chromosome 7.
Two healthy parents, heterozygous for cystic fibrosis, have a child that does not have cystic fibrosis. They are planning to have a second child.
Using a Punnett square, determine the probability of their second child being born with the condition. Use
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a. Punnett square:
Probability of 2nd child having cystic fibrosis = 25%.
b. Deletion of nucleotides in CFTR gene:
→ Three mRNA nucleotides (a codon) spell out instructions for one amino acid. The deletion here stretches across two codons that normally code for isoleucine and phenylalanine.
→ At first glance, you’d expect losing nucleotides from both codons would mess up both amino acids.
→ In isoleucine however, multiple different triplet codes can signal for its production. Its original code was AUC and after the deletion it became AUU – which still makes isoleucine.
→ Only phenylalanine gets knocked out of the protein sequence, while isoleucine stays put thanks to its flexible coding options.
a. Punnett square:
Probability of 2nd child having cystic fibrosis = 25%.
b. Deletion of nucleotides in CFTR gene:
→ Three mRNA nucleotides (a codon) spell out instructions for one amino acid. The deletion here stretches across two codons that normally code for isoleucine and phenylalanine.
→ At first glance, you’d expect losing nucleotides from both codons would mess up both amino acids.
→ In isoleucine however, multiple different triplet codes can signal for its production. Its original code was AUC and after the deletion it became AUU – which still makes isoleucine.
→ Only phenylalanine gets knocked out of the protein sequence, while isoleucine stays put thanks to its flexible coding options.
Milk pasteurisation (heating to approximately 70°C) was gradually introduced in America from the early 1900s. The graph shows the number of disease outbreaks in relation to raw (unpasteurised) and pasteurised milk in America from 1900-1975.
Explain the trends observed in the graph. In your response, refer to the role of Pasteur's work in pasteurisation. (5 marks)
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→ Louis Pasteur’s research was pivotal in debunking the theory of spontaneous generation and establishing our understanding of microorganisms.
→ His work revealed that microbes present in milk could be responsible for disease outbreaks.
→ He demonstrated that exposing substances to high temperatures effectively kills microorganisms, which is why heating milk to 70°C eliminates many harmful bacteria.
→ This scientific foundation – the presence of microbes in milk and their vulnerability to heat – explains the effectiveness of milk pasteurisation in preventing disease outbreaks.
→ The historical data presented in the graph supports this, showing significantly fewer disease outbreaks linked to pasteurised milk compared to raw milk.
→ A notable decline in raw milk-related outbreaks occurred after 1945, though this may also be attributed to decreased raw milk consumption during that period.
→ While pasteurised milk has generally proven safer, some disease outbreaks have still occurred with pasteurised products. These cases typically result from issues in the pasteurisation process itself or problems during subsequent storage and transportation of the milk.
→ Louis Pasteur’s research was pivotal in debunking the theory of spontaneous generation and establishing our understanding of microorganisms.
→ His work revealed that microbes present in milk could be responsible for disease outbreaks.
→ He demonstrated that exposing substances to high temperatures effectively kills microorganisms, which is why heating milk to 70°C eliminates many harmful bacteria.
→ This scientific foundation – the presence of microbes in milk and their vulnerability to heat – explains the effectiveness of milk pasteurisation in preventing disease outbreaks.
→ The historical data presented in the graph supports this, showing significantly fewer disease outbreaks linked to pasteurised milk compared to raw milk.
→ A notable decline in raw milk-related outbreaks occurred after 1945, though this may also be attributed to decreased raw milk consumption during that period.
→ While pasteurised milk has generally proven safer, some disease outbreaks have still occurred with pasteurised products. These cases typically result from issues in the pasteurisation process itself or problems during subsequent storage and transportation of the milk.
The diagram represents some experimental steps used in the production of large amounts of human growth hormone.
What makes this technology successful?
→ The technology is possible because restriction enzymes create compatible sticky ends on both the bacterial plasmid and human DNA containing the growth hormone gene.
→ This allows them to be joined together via complementary base pairing before DNA ligase permanently connects them, which is essential for successful gene transfer.