HSC Physics

Why choose HSC Physics

HSC Physics can be one of the most rewarding HSC subjects that is widely and commonly available across schools in NSW. HSC Physics tends to appeal to students with an interest for quantitative subjects like mathematics. In fact, if one is to try to define physics, it would be applied 2 unit maths. The mathematics in physics is certainly not difficult, but the problems in Physics are structured in terms of real-world applications. Therefore students who have a keen interest in the physical world and the theory behind its behavior are advised to take physics.

In terms of scaling, HSC physics has always scaled quite decently. Traditionally and in recent years, physics has had a scaled mean of about 29/50, meaning it scales slightly under HSC Chemistry, English Advanced and Economics. However physics has always scaled significantly better than biology, which is convenient since HSC Physics and Chemistry has always had a synergy about them. They are to a large extent similar courses, both requiring a similar skillset from students who want to do well. However, unlike HSC Chemistry, Physics is less experience-based, as there are less things upon which we need to refer to repeatedly throughout the course. ( For example, in Chemistry, we had to know the common valencies, solubility rules, how to name carbon compounds etc)

Instead, Physics requires more of an ability to imagine things yourself and conduct what we call 'thought experiments' in your own mind in order to understand the concepts taught in the course. This is more of a skill rather than a set of knowledge. For example, to gain a solid grasp of Einstein's theory of special relativity and the associated equations, it is all about your ability to get your head around how time dilation operates in different frames, and in relation to each other. While theory helps and rote-learning the method of applying the equations, this approach is limited in its usefulness since slightly tricky exam questions can easily throw you off.

How to master HSC Physics

To get better at HSC Physics, since many things are very abstract and conceptual (e.g. to understand how an induction motor actually works, or Einstein's equations of time and mass dilation, or the cause of striation patterns in vacuum tubes), it is a good idea to ask a teacher or tutor as many questions as possible. That means whenever there is some concept that you don't understand, or even a tiny point within a wider concept, don't leave it alone. You should ask all questions until you have a concrete understanding of the concept in question before moving on.

A good way is to constantly test your own knowledge by connecting all the related concepts together and seeing if there are any contradictions that a revealed by connecting up what you know. This is because physics is very conceptual in nature, and slightly different to the other sciences (Chemistry and Biology). Physics revolves around understanding abstract concepts, most of which can not be experimentally tested within a school lab, and some concepts can never be properly experimentally tested (e.g. whether the luminiferous aether really exists).

Successful physics students have a great ability to conduct thought experiments. What this involves is essentially testing out an idea in your mind, following physical rules you have learnt, to see whether you arrive at a conclusion that is absurd, or plausible. It's difficult to truly understand this technique and to what extent we use it when thinking about concepts in Physics, but it is a good habit to always do this in order to verify and test your own understanding.

Good students would also have the ability to unify their understanding of various seemingly unrelated topics. One thing unique about HSC physics as opposed to other HSC sciences is that its topics are all latently linked, and based on a common set of fundamental physical principles. What we mean by 'latent' is that these links are not immediately visible, and the ability to draw these links is what separates a student who gets 95+ in their HSC mark, versus a student who doesn't. For example, the same set of rules apply to forces on a cathode ray as those that are responsible for the motor effect. And it is the same principle (electromagnetic induction) which explains why magnetars (if you do Astrophysics) have such intense magnetic fields. This is the same line of thought that led Sir Isaac Newton to conclude that it is the force of gravity which keeps the Moon in a circular or bit around the Earth.

Different ways of thinking about one concept

For example, think of an induction motor: we are all taught by teachers that such a motor works because the squirrel cage 'chases' the spinning magnetic field, citing Lenz's law. However what if you totally ignore your knowledge about Lenz's law, can you try to explain how an induction motor works solely by using the right-hand push rule? Well actually you can, because as the magnetic field sweeps past a part of the squirrel cage, that's like having a current move towards the opposite direction, which imparts a force along the cage onto the positive charge carriers as per the direction of your palm. This dictates the induced current flow, and if you then shift your thumb to point towards this current, you'll notice the palm now points towards the direction the magnetic field was moving towards. In effect, the cage actually does 'chase' the field, however as you can see, we can explain it in terms of first principles rather than rely on sweeping statements like 'induction motors work because of Lenz's law'.

Another practical example highlighting the same point is attempting to explain the concept of an event horizon in terms of escape velocity. Without going into too much detail, recall that there is a formula to find escape velocity from a body of mass, and that it is inversely proportional to r, the distance from the centre of that mass. For black holes, since mass is all focused within a singularity of infinite density, there comes a point where r is sufficiently small that escape velocity reaches, then exceeds c, the speed of light. At the point where r makes the escape velocity exactly equal to the speed of light, this defines the boundary of the event horizon, beyond which no information can escape. If we further decrease r (i.e. get closer to the black hole), by then the calculated escape velocity exceeds c, and from Einstein's mass dilation equations, this could never physically be achieved. Therefore this is a more practical and unified way of thinking about the concept of black holes and why they have an event horizon.

As a student aiming for 95+ (HSC aligned mark) in HSC Physics, without a doubt, your depth of knowledge, and the extent of drawing connections between your conceptual understanding, will determine whether you will reach your goal of 95+. That is, your ability to unify your understanding of the various topics of physics will help you significantly when it comes to showing depth in your understanding in exam responses.