How to Answer 'Explain' Physics Questions | HSC Physics Key Verb Series Part 1
Answering ‘Explain’ long-response Physics questions
Don’t know why or where you are losing marks in extended response questions? Most Year 11 and 12 Physics students find answering ‘explain’ Physics questions difficult and challenging.
‘How to answer ‘Explain’ Long Response Questions’ is a comprehensive guide for Year 12 students on how to develop logical, sequential and coherent answers to extended response questions requiring you to ‘Explain’.
In this article we discuss:
- Types of explain questions in the HSC Physics Exam
- The process for answering ‘Explain’ Physics questions
- Sample explain questions and answers using the CEO Framework
Types of explain questions in the HSC Physics Exam
‘Explain’ questions make up a significant proportion of your HSC Physics exam mark, and is critical to achieving a Band 6 result.
In the 2019 HSC Physics Exam, ‘Explain’ questions accounted for 22 marks. That’s 22% of the total exam mark!
Marks allocated for an ‘explain’ question can vary from 2 to 7 marks. Examples of explain questions with different marks are listed below.
| Question | Marks |
| Explain how the total energy of the rocket changes as it is being launched from the surface of Earth | 2 |
| Explain why an electron follows a circular path when it moves perpendicular to a uniform magnetic field. | 3 |
| Explain how inertial and non-inertial frames of reference relate to the principle of relativity. | 3 |
| Max Planck’s hypothesis on the nature of light was able to account for the experimental curve for blackbody radiation. Explain. | 4 |
| Explain how the analysis of quantitative observations contributed to the development of the concept that energy is quantised. | 7 |
What is the process for answering ‘Explain’ Physics questions?
To answer ‘explain’ physics questions, you must first understand the meaning of the verb, ‘explain.
The NSW Education Standards Authority defines ‘Explain’ as “relating cause and effect, making the relationship between things evident; provide why and/or how.”
When answering ‘explain’ questions, students are required to relate the cause and effect using scientific arguments. In addition, the response needs to be presented and structured in a logical and sequential manner.
One of the methods for answering ‘Explain’ questions is using Learnable’s CEO FrameworkTM (Cause, Effect, Outcome) to construct a logical and sequential response.
Learnable CEO FrameworkTM
The CEO Framework helps you structure your answer and meet the marking criteria for ‘explain’ questions. View the 3 step process below.
| Step | CEO Framework | Detail |
| 1 | Cause | Identify the cause |
| 2 | Effect | Describe the effect (due to the cause) by referring to the relevant law of Physics. |
| 3 | Outcome | State the outcome. |
When answering ‘Explain’ questions, you must include a reference to a relevant Law of Physics where possible.
Sample ‘explain’ Physics questions and answers using the CEO FrameworkTM
Let’s apply Learnable’s CEO Framework to answer the two types of ‘explain’ Physics questions.
- Explain why
- Explain how
Question 1 (3 Marks): Module 6
Explain why an electron follows a circular path when it moves perpendicular to a uniform magnetic field.
Solution
Step 1: Identify the cause.
In this question, the cause must relate to the forces a charged particle experiences when moving in a magnetic field.
| Step | CEO Framework | Detail |
| 1 | Cause | An electron moving perpendicular to a uniform magnetic field experiences a constant magnetic force {(F = qvB),} which is always perpendicular to the electron’s velocity. |
Step 2: Describe the effect due to the cause.
Our effect must derive the relationship between the force acting on the charged particle in a magnetic field and the charged particle’s circular path. It must link these two points using a scientific argument.
| Step | CEO Framework | Detail |
| 1 | Cause | An electron moving perpendicular to a uniform magnetic field experiences a constant magnetic force {(F = qvB),} which is always perpendicular to the electron’s velocity. |
| 2 | Effect | Therefore, the magnetic force acts as the centripetal force. |
Step 3: State the outcome.
Our outcome must be a direct result of the effect outlines in Step 2.
| Step | CEO Framework | Detail |
| 1 | Cause | An electron moving perpendicular to a uniform magnetic field experiences a constant magnetic force {(F = qvB),} which is always perpendicular to the electron’s velocity. |
| 2 | Effect | Therefore, the magnetic force acts as the centripetal force. |
| 3 | Outcome | Hence, the electron undergoes uniform circular motion and follows a circular path. |
Step 4: Construct a logical and sequential response.
A sample response to the question using the CEO FrameworkTM is shown below.
An electron moving perpendicular to a uniform magnetic field experiences a constant magnetic force with magnitude F = qvB , which is always perpendicular to the electrons velocity. Therefore, the constant magnetic force acts as a centripetal force. Hence, the electron undergoes uniform circular motion and follows a circular path.
The sequential links between cause, effect and outcome are bolded in our sample answer. This ensures our answer features a logical argument from start to finish.
Question 2 (3 Marks): Module 7
Explain how inertial and non-inertial frames of reference relate to the principle of relativity.
Solution
In this question, students are asked to relate the principle of relativity (cause) to inertial and non-inertial frames of reference (effect).
| Step | CEO Framework | Detail |
| 1 | Cause | The principle of relativity states that it is not possible to detect motion with uniform velocity while in one frame of reference without referring to another frame of reference. |
| 2 | Effect | Therefore, the principle of relativity only applies for non-accelerating steady motion, which occurs in an inertial frame of reference. Within an inertial frame of reference, experiments or observations cannot be performed that would indicate whether an object is stationary or moving with constant velocity. |
| 3 | Outcome | Hence, the speed of light is constant in inertial frames of reference which lead to time dilation, length contraction, etc. |
A sample response to the question using the CEO FrameworkTM is shown below.
The principle of relativity states that it is not possible to detect motion with uniform velocity while in one frame of reference without referring to another frame of reference.
Therefore, the principle of relativity only applies for non-accelerating steady motion, which occurs in an inertial frame of reference. Within an inertial frame of reference, experiments or observations cannot be performed that would indicate whether an object is stationary or moving with constant velocity.
Hence, the speed of light is constant in inertial frames of reference which lead to time dilation, length contraction, etc.
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Written by DJ Kim
DJ is the founder of Learnable and has a passionate interest in education and technology. He is also the author of Physics resources on Learnable.
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