Physics 2019 HSC exam pack

Students should:

• be able to plot graphs and describe the relationship between the data displayed in a graph and the relevant concept
• be able to extract quantitative relationships from graphs including the use of a line of best fit
• describe directions of forces clearly
• clearly label diagrams to support answers
• show clear cause and effect relationships in explanations
• show complete working including full substitution into relevant formulas
• be familiar with the SI units of all relevant quantities and the relevant prefixes and their abbreviations
• be able to derive mathematical relationships, including the use of vector analysis
• be familiar with key physical principles such as conservation laws and Laws of motion and be able to apply them in a range of contexts
• be able to discuss how a range of models are applied in Physics and the evidence used to validate them
• be able to describe historical experiments that contributed to a new understanding of physical concepts
• refer to the stimulus material in answering questions where this is stated
• clearly indicate when a response is contained in a  different booklet.

Question 21

In better responses, students were able to:

• identify that electrons have a wave nature and include an equation related to the electron’s de Broglie wavelength.

Areas for students to improve include:

• distinguishing between the work of de Broglie and Bohr.

Question 22

In better responses, students were able to:

• show how the variation in spectra provides information about two features of stars.

Question 23

In better responses, students were able to:

• plot data from a results table onto a graph with axis of different scales
• draw a correct straight line of best fit
• extrapolate the line of best fit to determine the KE (max) intercept as the work function of the metal.

Areas for students to improve include:

• identifying the line of best fit as the line that bisects the plotted points evenly
• understanding that the work function of a metal is the extrapolated KE_(max) value where frequency= 0 on the KE_(max) v frequency graph.

Question 24

In better responses, students were able to:

• calculate the output power and identify that there is a loss of energy (a)
• identify and explain how each specific modification reduces energy loss or improves magnetic flux linkage (b).

Areas for students to improve include:

• including calculations when specified in the question and showing full working
• stating the specific modifications in the explanations
• reading the question carefully and ensuring their response address the specific stimulus provided.

Question 25

In better responses, students were able to:

• clearly state a prediction of Maxwell and make a very direct relation to the model provided in the question
• identify and clearly name E as an electric field and B as a magnetic field - not just simply waves
• label or annotate the diagram provided to clarify their response.

Areas for students to improve include:

• avoiding simply rephrasing the question
• clearly stating the link and/or comparison made to the diagram.

Question 26

In better responses, students were able to:

• explain how features of the graph justified the validity of the student’s model (a)
• use a mathematical analysis of the graph to support their answer (a)
• justify the decrease in accuracy of the model for angles beyond 25°using an alternate mathematical model, T = Fr sin ϴ (b)
• support the alternate model with a mathematical analysis for angle well beyond 25° (b).

Areas for students to improve include:

• avoiding the use of generalised discussions of validity rather than specifically addressing the scenario (a)
• the difference between the two torque formulas on the formula sheet (b)
• recognising that a mathematical formula is a type of model that can be used to make predictions (b).

Question 27

In better responses, students were able to:

• clearly state different frames of reference, identify that the speed of light is constant, and link this to time dilation(a)
• state the results of a known experiment (b).

Areas for students to improve include:

• recognising that Twin paradox is not considered an appropriate thought (a)
• being clear about the meaning of dilation in terms of the different frames of reference (a)
• being fully familiar with specific experiments and how the results have supported Special Relativity (b).

Question 28

In better responses, students were able to:

• state that both the direction and magnitude of the force on WX remains unchanged throughout the rotation
• indicate that the force on XY was initially zero, and that both the magnitude of the force increases and indicate that the force was to the right.

Areas for students to improve include:

• reading the question carefully to ensure they are addressing the correct sides of the coil
• using clear unambiguous language when indicating directions of forces, such as down into the page, up the page, not just up or down
• ensuring that the correct concept is being analysed, in this case forces rather than torque.

Question 29

In better responses, students were able to:

• state the factors involved and identify the relevant formulas to use
• show clear and systematic working.

Areas for students to improve include:

• ensuring familiarity with all the pronumerals used in the formula sheet and not to confuse similar terms for example: V(voltage)with v (velocity).

Question 30

In better responses, students were able to:

• demonstrate an understanding of the conversion of potential energy to kinetic energy (a)
• identify the relevant equations and correctly substitute into them (a)
• demonstrate a clear understanding of projectile motion (b)
• identify relevant equations and correctly substitute into them (b).

Areas for students to improve include:

• identifying situations in which acceleration is not constant (a)
• manipulating equations to solve for an unknown variable (a)
• identifying when velocity vectors need to be resolved into their components (b).

Question 31

In better responses, students were able to:

• provide explanations for changes on the spring balance for two distinct time periods (a)
• refer to balanced and unbalanced forces (a)
• apply Newton’s third Law of motion (a)
• assess the features of the prediction as having parts that are both inaccurate and accurate and relate to the  production of back emf (b).

Areas for students to improve include:

• explaining more than one change on the spring balance (a)
• identifying explicitly the direction of change of the spring balance reading (a)
• recognising that assessing a prediction entails making a judgment about its correctness or otherwise (b)
• explaining how back emf affects operating current in a motor (b).

Question 32

In better responses, students were able to:

• correctly describe an experiment and how it improved our understanding for both the electron and another fundamental particle.

Areas for students to improve include

• correctly identifying a fundamental particle, noting that protons and neutrons are not fundamental particles.

Question 33

In better responses, students were able to:

• explain the particle motion in terms of their trajectories rather than just the forces the particles experienced in the field
• explain the difference in radius between the particles by equating centripetal force with magnetic force
• explain that the particles experienced uniform circular motion due to a perpendicular force rather than just being deflected.

Areas for students to improve include

• discerning between different types of fields and the shape of trajectories within them
• understanding that both the mass and charge together affect the radius of curvature
• being clear when describing the direction of particles deflection.

Question 34

In better responses, students were able to:

• answer the all parts of the question using the stimulus material
• draw links between each element and provide a response that was clear and logically written
• clearly state that Proton - Proton chain was the dominant production of energy
• outline that energy comes from the conversion of mass
• correctly calculate energy and temperature and show working.

Areas for students to improve include:

• understanding units
• planning the response to ensure that all parts of the question are addressed.

Question 35

In better responses, students were able to:

• recognise that the car was moving with uniform circular motion
• use vector analysis to derive a relevant relationship.

Areas for students to improve include:

• reading all the material in the question to ensure that the correct scenario is being analysed
• showing all steps in the derivation of an equation.

Question 36

In better responses students were able to:

• correctly calculate the mass defect and hence the kinetic energy of the alpha particle
• recognise that the Law of Conservation of Momentum would apply to the decay products
• use equations for momentum and kinetic energy to explain why the larger velocity of the alpha outweighs its smaller mass in determining its kinetic energy compared to the polonium.

Areas for students to improve include:

• being able to convert from mass to energy using the appropriate units
• applying conservation of momentum in an unfamiliar context.