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### AuthorTopic: Paulsterio's Year 12 Physics Guide  (Read 17381 times) Tweet Share

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#### paulsterio

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##### Paulsterio's Year 12 Physics Guide
« on: December 27, 2011, 06:10:07 pm »
+10
So no physics guide as of yet and nobody seems to be writing one, so I thought I'll get the ball rolling.
A little bit about myself first, I graduated from year 12 in 2011 with a study score of 46 in Physics.

Scored: 159/180 for Unit 3 and 179/180 for Unit 4 in Exams

Physics is extremely competitive, so unlike subjects like Biology, where you can afford to lose about 4 marks per exam and still get a 50, the margin for physics is probably around 1 mark per exam, maybe 3 marks in total if you have really strong SACs (i.e. 100/100 for SACs). You could even get away with losing 4 marks in total with 100% SACs (Thushan got 172/180 for Unit 3 and pulled off a 50). So physics, therefore, is really about how to minimise errors and not lose marks on explanations. Physics examiners are probably a little bit more relaxed than say Biology examiners in that your explanations need to be logical and mathematical rather than worded in a certain way. If you answer makes sense, then you are on track to gain full marks for that part.

Alrighty, so let's start off with Unit 3

Unit 3 consists of two core areas and one detailed study. The core areas are Motion and Electronics/Photonics. The detailed studies are Relativity, Structures/Materials and Further Electronics.

I completed Further Electronics in Unit 3 and was really dogged out by a really hard Further Electronics exam that lost me a lot of marks. You don't really have a choice here because your school picks the study for you, although I do suggest that you learn an extra detailed study, make sure you are "exam quality" for the extra one you learn though, then you can make a choice during reading time. That's what I did for Unit 4, and it was much better, detailed studies are relatively easy (usually) compared to the core work.

AOS 1 - Motion
Motion is probably the most difficult area in Unit 3 physics. There's not many explanations, but there's a lot of calculations.
In terms of explanations, make sure you can explain simple things such as:
• Conservation of Energy
• Conservation of Momentum
• Why we can accelerate more if we are on an banked road compared to a flat road
• Elastic and inelastic collisions
• Apparent weightlessness compared to true weightlessness
• Other things, which I'll add as soon as I remember
Now, the tricky part about motion is the calculations, there's two ways to approach the calculations. You can either do it using first principles or you can do it by formulae.
If you choose to do it using first principles, you will do things such as this:
• Find the maximum acceleration on a banked curve? You will resolve the forces and find the maximum friction force...etc and arrive at the answer
• Find the acceleration down an inclined plane? You will resolve parallel to the plane and get F = mgsin(theta) -> a = gsin(theta)
So doing it via first principles always works, but sometimes, it's tricky and I personally am not a fan of it, I prefer the safer way, which is to use formulae. If you wish to use formulae, you will have to spend some time sitting down on a weekend, probably in the April holidays when you've finished motion to write up your formulae sheet (you're allowed 1 double sided A4 page, use 1 side for motion). Now you can always use general cases to solve for commonly found values, so that all you basically have to do is substitute in your values and you get the answer.
For example:
• Projectile motion is "quadratic" so you can technically find the flight time by solving the general case of the quadratic equation
• Similarly, projectile motion can be solved by using formulae as well
I will modify this with my list of motion formulae when I dig up my formula sheet, you'll understand more about it, hopefully, when that's up - give me a few days

AOS 2 - Electronics and Photonics
This is probably two distinct studies in one. Electronics is relatively easy and most will probably find it quite easy. You only really have to know the basic electronics formulae such as V = IR, P = VI and associated power formulae, you will have to understand voltage dividers, which can be solved using the formula found in textbooks or by first principles (finding the current), you will also have to know about amplifiers. Most of the calculations here are easy, but circuit analysis can be quite tough sometimes, especially when diodes are involved, but stick to your principle of "Parallel = Same Voltage" and "Series = Same Current" and you should be able to knock them down. Now over to the photonics section, this is just really explanations, you have to understand about modulation and associated terms as well as probably how to transfer these principles to the transfer of information via fibre optic systems. You'll also have to analyse circuits with added photonic devices, i.e. LDRs, LEDs, LDs, Photodiodes.
In terms of explanations, make sure you can explain these key concepts:
• Modulation/Demodulation
• Terms to do with Modulation - Carrier wave, signal wave...etc
• Whether an increase in light (or temperature) or whatever will cause in an increase in voltage across a particular resistor in a Voltage Divider
• Explain whether a switching circuit (e.g. air-con/heater) is designed properly (voltage divider) and if not, why?
• Explain how data is transmitted in a photonic system
• Clipping, distortion, cut-off and saturation of amplifiers

AOS 3 - Detailed Study
Relativity (By Laseredd)

So, in my opinion, the special relativity detailed study was the most interesting part of Unit 3, if not the entire course. You're exposed to ideas that are fairly out there - coming across things like "two events that occur simultaneously in different places in one frame of reference may occur at different times in another frame of reference" will probably make you think . But that shouldn't be a problem, once you get your head around the key concepts, it's actually seems quite simple and in a weird way, almost "intuitive".

Without a doubt, the most important thing about this detailed study are the concepts. You need to realise that there are a few key principles to the ideas and that the rest are just consequences. The meat of special relativity are the two postulates, which always seem to be differently worded everywhere you read (but the ideas always stays the same). You need to thoroughly understand what these two postulates are. You need to spend time getting your head around the idea of reference frames. You need to understand the consequences of special relativity (the ones that are covered in VCE Physics anyway): time dilation, length contraction, simultaneity, relativistic mass/momentum, mass-energy equivalence (not a complete list).

There's other stuff I've neglected to mention: the history aspect of the study, where you are introduced to how the theory came to be developed (Newton/Galileo, the "aether", Michelson-Morley experiment, what Maxwell discovered etc.). That stuff is fairly straight forward, but still something that needs to be understood (almost always will there be a question about the Michelson-Morley experiment).

Why am I going on about understanding the concepts so much? Besides from being a very theory heavy area of study, the calculation part is quite simple - but it depends on being able to differentiate between reference frames etc. So all that complicated stuff boils down to 12 or 13 pretty simple questions. The detailed studies are multiple choice, which allows you to quickly eliminate a few answers. This is handy, since you will probably only allocate 20 - 25 minutes for the detailed study. For most questions, this is very easy in relativity, since if you know your theory you can tell that one of the given answers is talking about the wrong reference frame or that it violates one of the postulates etc.

About the calculations, it's mostly dealing with subbing in values into simple equations. This goes for everything else in VCE Physics, but ensure you know how to use your scientific calculator well. However, you do need to do a lot of transposing (may be a good idea to pre-transpose a few of the equations for your cheat sheet), so you should be able to quickly transpose this: $\gamma = \frac{1}{\sqrt{1-\frac{v^2}{c^2}}}$ for 'v' with no troubles.

Oh and also, you don't need to show working for the detailed studies, but you're given enough space to do calculations on the page. It's definitely worth doing some amount of working in case you come back to check over your work.

Structures and Materials
Now I'm gonna need some assistance here, anyone who has done these two detailed studies and want to write a guide, feel free to, I'll add it onto here

Further Electronics
This is an alright detailed study, not too hard, not too easy, it uses a lot of skills which have already been learnt from the other sections. It's centred around rectifying an AC voltage into smooth, stable DC. You'll have to be familiar with a bridge rectifier, capacitor, zener diode (and also IC voltage regulator). Essentially you will also have to know a little bit about CROs and how to read their outputs. You'll also have to know what the output of a bridge rectifier would look like (kind of like an absolute sine function), output after a capacitor as well as output after the zener diode. You should be able to calculate time constants and ripple voltage from the standard formulae. All of the questions are Multiple Choice which should make it a little easier or harder depending on whether you like MC.

• You should be aiming to do about 20 practice exams for physics
• Note your mistakes and don't make them again
• If you're aiming for a 45+ study score, you should be aiming to really finish the whole paper in about 1 hour and 15 minutes.
• You should also be getting all numerical (calculation) questions right as well as getting the explain questions mostly correct.
• You should aim to really get 100% on the Detailed Study, this means that a mark lost due to an incomplete explanation will not be so costly
• Remember to reason using a formula during explanations, it usually works and it's an easy way to explain a lot of concepts.
• Double check numerical questions.
• Write your formula sheet early on in the year, and improve on it whilst you do practice exams, include what you don't know, don't waste space including what you already know and won't be referring to in the exam.
• Work out a specific order and stick to it, (my order was Motion, Electronics, Detailed Study)
• Make sure your calculator has battery, change it before the exam if you're pedantic.
• Remember to bring a pencil for the Multiple Choice
• When doing practice exams, don't rush, give yourself 1 hour and 15 minutes, don't try to finish it in 45 minutes if you're making careless errors.
• Make "model answers" for typical exam explain questions
« Last Edit: July 22, 2012, 12:26:54 am by thushan »

#### paulsterio

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##### Re: Paulsterio's Year 12 Physics Guide
« Reply #1 on: December 27, 2011, 06:11:38 pm »
+4
Ok, so now onto Unit 4, I've always personally found that Unit 4 is a lot harder than Unit 3, it introduces many more new concepts, which are slightly less intuitive. Most of Unit 3, Motion and Electronics, are really just extensions of what's in year 11, but in Unit 4, both the Electric Power and Light/Matter components are new (although light was done in Year 11, it's not really that relevant to Year 12 - you won't need Snell's law or anything like that).

Similar to Unit 3, the two core area of studies will be different. Electric power will mostly be mathematical questions with few explanations whilst Light/Matter will be mostly explanation with a few mathematical questions. The three detailed studies for Unit 4 are Synchrotron, Photonics and Sound. I did both Photonics and Sound, but completed Photonics in the Exam as it was far easier (in my opinion and judgement).

AOS 1 - Electric Power
This is the most difficult area of study in all of Year 12 physics, I found it difficult in that the concepts weren't too bad, but some of it was just downright confusing. You should be familiar with the formulae, all of which are relatively easy to apply. The challenge in Electric Power comes from concepts involved. You'll have to have a good understanding of the hand rules, the Grip Rule and Slap Rules (or other variations which you might like to use). Motors and the like are all relatively easy. You also have to understand the concepts of magnetic flux and induced voltage. You generally have to be able to explain the following things:
• Draw magnetic field lines
• Difference between slip rings and a split ring commutator
• Where you would use slip rings or a split ring commutator
• Explain why you want to use a high voltage for transmission
• Explain why transformers only work with AC (explain it using change in flux = induced voltage, DC produces no change in flux)
• Explain ways to reduce power loss during transmission
• Draw a graph of voltage given the graph of flux
• Draw a graph given the rotational period (and other info) of a rotating loop

AOS 2 - Light and Matter
To sum up Light and Matter, it's extremely abstract. There's very little maths, although you have to be able to calculate things such as the Work Function, or the energy required to remove an electron from a certain metal (and other photoelectric effect type calculations). You also have to be able to draw graphs for the photoelectric effect as well as interpret energy level diagrams for an atom (or draw them). You might also have to draw standing waves around an atom to show how electrons moved. Then there's calculation of momentum of a photon or the de Broglie wavelength of an animate particle. You will have to be able to explain the following things:
« Last Edit: December 30, 2011, 06:14:30 pm by paulsterio »

#### paulsterio

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##### Re: Paulsterio's Year 12 Physics Guide
« Reply #2 on: December 27, 2011, 06:12:21 pm »
0
Reserved - Extra info

#### Aurelian

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##### Re: Paulsterio's Year 12 Physics Guide
« Reply #3 on: December 27, 2011, 06:20:06 pm »
+3
...although I do suggest that you learn an extra detailed study, make sure you are "exam quality" for the extra one you learn though, then you can make a choice during reading time. That's what I did for Unit 4, and it was much better, detailed studies are relatively easy (usually) compared to the core work.

This is really unnecessary... I would strongly recommend against this D=
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#### Hellrocks

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##### Re: Paulsterio's Year 12 Physics Guide
« Reply #4 on: December 27, 2011, 06:54:24 pm »
0
In Paul's case it was necessary because the 'odd' detailed studies is quite ridiculous sometimes. Unless your part of the majority which does the 'common' detailed studies, you might get screwed over by the small detailed studies.

#### paulsterio

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##### Re: Paulsterio's Year 12 Physics Guide
« Reply #5 on: December 27, 2011, 07:08:54 pm »
0
If you stick with Structures/Materials and then Sound you should be fine, because around 80% or so of the state do it (not sure of the exact number, it's on the examiner's report I think) - but anyway, if you get a hard one of them, it will be ok because it's hard for 80% of the state. If you do Further Electronics say, like I did, around 10% of the state or so do it and cause it was a lot harder than Structures, I fell behind heaps, so it's happened to me

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##### Re: Paulsterio's Year 12 Physics Guide
« Reply #6 on: December 27, 2011, 08:04:26 pm »
+2
Seems like pretty good advice Paul Not too sure about the doing a separate detailed study, but I wasn't in a situation where that was necessary (did special relativity and sound).

Something that you didn't explicitly mention, which is probably pretty obvious (but still worth mentioning nonetheless), is that while you can use short-cut formulae, it's a risk if you don't thoroughly understand the "first principles" method or if you don't know the limitations of the formulae (for examples, those projectile motion ones are the really obvious case here regarding limitations).

Learning the "first principles" method is probably the way you'd go for learning the concept in the first place. I'd also emphasise that it's pretty much always worth spending the time to look at some form of derivation for every formula you come across in Unit 3/4 Physics. I found it helped me a lot for understanding what a formula was going on about etc.

#### Deceitful Wings

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##### Re: Paulsterio's Year 12 Physics Guide
« Reply #7 on: December 27, 2011, 08:08:36 pm »
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How many marks can you lose to afford to get a study score above 45?

#### paulsterio

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##### Re: Paulsterio's Year 12 Physics Guide
« Reply #8 on: December 27, 2011, 08:13:19 pm »
0
Something that you didn't explicitly mention, which is probably pretty obvious (but still worth mentioning nonetheless), is that while you can use short-cut formulae, it's a risk if you don't thoroughly understand the "first principles" method or if you don't know the limitations of the formulae (for examples, those projectile motion ones are the really obvious case here regarding limitations).

Hmm, that's true actually, I guess I never really got my head around some things such as banked curves, but I just made up some custom formulae and it's always worked for me, but you do raise a really good point, you do have to understand what the formula means and how it's derived.

How many marks can you lose to afford to get a study score above 45?

You're welcome
Well I got 159/180 and 179/180, so I lost 22 marks, and when you halve that, it's 11 marks, so I guess you could probably lose around that much and get a 45, I had 100/100 for SACs, however. So that would have also played a part, but I think 10 marks lost in total should be ok for a 45+

#### max payne

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##### Re: Paulsterio's Year 12 Physics Guide
« Reply #9 on: December 27, 2011, 08:58:02 pm »
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correct me if i'm wrong but i believe 159 and 179 is better than 169 and 169
Assuming that grades are not linearly distributed then thats probably true...although I'm not sure

#### paulsterio

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##### Re: Paulsterio's Year 12 Physics Guide
« Reply #10 on: December 27, 2011, 09:25:59 pm »
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it's true because the GA's are individually standardised, because grades are normally distributed, losing one mark near the middle will put you back a lot more than losing one mark near the top end (that's what I think anyway)

#### pi

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##### Re: Paulsterio's Year 12 Physics Guide
« Reply #11 on: December 28, 2011, 10:28:40 am »
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##### Re: Paulsterio's Year 12 Physics Guide
« Reply #12 on: December 28, 2011, 10:30:45 am »
+5
AOS 3 - Detailed Study
Relativity
Structures and Materials
Now I'm gonna need some assistance here, anyone who has done these two detailed studies and want to write a guide, feel free to, I'll add it onto here

Detailed Study 1: Einstein's Special Relativity

So, in my opinion, the special relativity detailed study was the most interesting part of Unit 3, if not the entire course. You're exposed to ideas that are fairly out there - coming across things like "two events that occur simultaneously in different places in one frame of reference may occur at different times in another frame of reference" will probably make you think . But that shouldn't be a problem, once you get your head around the key concepts, it's actually seems quite simple and in a weird way, almost "intuitive".

Without a doubt, the most important thing about this detailed study are the concepts. You need to realise that there are a few key principles to the ideas and that the rest are just consequences. The meat of special relativity are the two postulates, which always seem to be differently worded everywhere you read (but the ideas always stays the same). You need to thoroughly understand what these two postulates are. You need to spend time getting your head around the idea of reference frames. You need to understand the consequences of special relativity (the ones that are covered in VCE Physics anyway): time dilation, length contraction, simultaneity, relativistic mass/momentum, mass-energy equivalence (not a complete list).

There's other stuff I've neglected to mention: the history aspect of the study, where you are introduced to how the theory came to be developed (Newton/Galileo, the "aether", Michelson-Morley experiment, what Maxwell discovered etc.). That stuff is fairly straight forward, but still something that needs to be understood (almost always will there be a question about the Michelson-Morley experiment).

Why am I going on about understanding the concepts so much? Besides from being a very theory heavy area of study, the calculation part is quite simple - but it depends on being able to differentiate between reference frames etc. So all that complicated stuff boils down to 12 or 13 pretty simple questions. The detailed studies are multiple choice, which allows you to quickly eliminate a few answers. This is handy, since you will probably only allocate 20 - 25 minutes for the detailed study. For most questions, this is very easy in relativity, since if you know your theory you can tell that one of the given answers is talking about the wrong reference frame or that it violates one of the postulates etc.

About the calculations, it's mostly dealing with subbing in values into simple equations. This goes for everything else in VCE Physics, but ensure you know how to use your scientific calculator well. However, you do need to do a lot of transposing (may be a good idea to pre-transpose a few of the equations for your cheat sheet), so you should be able to quickly transpose this: $\gamma = \frac{1}{\sqrt{1-\frac{v^2}{c^2}}}$ for 'v' with no troubles.

Oh and also, you don't need to show working for the detailed studies, but you're given enough space to do calculations on the page. It's definitely worth doing some amount of working in case you come back to check over your work.
« Last Edit: December 28, 2011, 11:21:57 am by laseredd »

#### paulsterio

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##### Re: Paulsterio's Year 12 Physics Guide
« Reply #13 on: December 31, 2011, 12:10:59 am »
+1
I guess this got superseded by Samad's guide oh well I'm nearly done so I'll finish off Unit 4 tomorrow

#### b^3

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