## Archive for the ‘Year 11’ category

### Looking through medical imaging

September 18, 2013

Well, this will be a quick unit. You might say that we will be only “looking through” it, rather than going for the full-on invasive surgery that we have done so far in our studies of motion.

The main purpose of this unit is to help you understand how we can use different types of radiation and other technologies to obtain information about the internal structures of objects or organisms that are not transparent to visible light.

When we have the ability to see into objects, it gives information that can be used to guide other choices – from determining the safety of a bridge (looking for microfractures in beams), to the integrity of a jet turbine or airscrew (checking to see for weaknesses that may result in catastrophic failure) or to diagnose medical conditions prior to surgery.

Your task for this unit is to select one of the following medical physics technology, and explain the basic physics behind what form of energy is used (define the type), how it is generated (if appropriate), how it interacts with material objects (how it is affected by passing through matter), how it is received (how the energy is collected and transformed so that the internal structure of what it passed through is made visible). You also need to discuss the advantages (what it allows the user to do) and disadvantages (what risks or dangers are inherent in the used of the technology).

### Physics is a *moving* science

July 21, 2013

Don’t start crying – it’s not about emotion, its all about motion. On second thoughts, you might want to cry after all – this unit we start pulling out the maths, and we just WON’T STOP! There is a lot to get done, and less time to do it in, but we’ve already talked about how much harder you are going to have to work this semester, so I won’t go into that any further.

The important thing to remember, when we are solving equations or drawing graphs is that PHYSICS IS NOT A MATHEMATICAL SUBJECT! Mathematics may be one of the techniques we use to model, analyse or predict what will happen in a situation, but the important thing is the concepts and theories underneath – you must understand the ideas below the mathematics. This is why the major task I have assigned to you so far is all about your “reading record”, not a list of questions. Keep in mind you must try and understand the “why” before you start analysing the “how” with the formulas.

This is not to say that you can ignore the mathematical components -NO! But it is equally important that you make sure that you understand both parts of the science – the Mathematical (data, formulas, graphs and equations) and the Conceptual (Theories, Laws and explanations).

### Ohm-o-Sapiens (evolved again!)

May 4, 2013

The human species is continuously evolving – from the early hominids such as Homo Robustus, through the Neanderthals, and eventually Homo Sapiens. Physics students (Genus: Ohm-o-Sapiens) are clearly a new advancement in the Human species, as shown by the ability to tolerate torment provided by Physics Teachers…

OK, enough jokes – what we are doing with this post is going beyond the prior posts on electric circuit theory, and into component analysis. We have already looked at Ohm’s Law, Kirchoff’s Laws, and Thevenin’s Law – these are all based on the simple concept of simple “ohmic components”. Such circuits are relatively simple to solve (except like ones to left, and this one) – you use the rules of parallel and serial circuit elements to simplify the problem, and solve using Ohm’s Law.

Some components are not that easy – they don’t follow the simple patterns of ohm’s law. These devices do not have a constant resistance for a variety of applied voltages – their characteristic Voltage – Current graphs show a curve, and this is something you must be able to describe, analyse and discuss.

### Join the Resistance!

April 26, 2013

It’s time to get into the hard stuff – It’s time to join the resistance! Don’t let the current events know watt you are thinking – charge it up and…

Ah damn – I can’t come up with a pun for voltage. I’m sure one of you can – If I groan or laugh I will swear off bad puns in class for a week. That should be enough of an incentive for all of you!

Well, this post is mainly a link to a prior post, and an updated list of videos. I will add a link to some class notes shortly, but here are the two main links you need:

See you all in class!

### And you thought Quadratics were bad…

April 21, 2013

So, we’ve gone through two and a bit chapters of Mathematical methods so far, and you are beginning to think that you’ve done the worst of it – it can’t get that much harder, can it? Really?

Well, welcome to cubics, quartics and higher order polynomials – they are the big brothers and sisters to the humble quadratic, and they’d like to have a word with you about beating up on their sibling, the poor little quadratic – something about “completing your square”

On a more serious note, if you are feeling alright about algebra so far, the next section isn’t any harder – just a few more ideas – nothing new or harder than we’ve done so far, just more. Just like when we started quadratics, the first thing we do with cubics and quartics  is to identify the common pattern, and be able to factorise them directly from recognising that pattern.

Once we can do that, we will look at how you can start to graph these functions from their intercepts – but that means we need a way of finding all the intercepts. We already knew from our studies of the Null Factor Law (NFL) that the factors of a quadratic equation can give the intercept. The Remainder theorem (right now, that irritating chorus should be going through your head) allows us to find the factors by finding values for a where f(a) = 0 for a given f(x). Combining all this knowledge gives us the ability to sketch almost any graph!

### Quixotic Quadratic Queries Qause Qonfusion

February 24, 2013

Welcome to Mathematical Methods – a subject which will prepare you for using mathematics to analyse the world and introduce the concept of developing theoretical models to investigate potential results of decisions. It is also a subject that will require you to work hard to master the skills and techniques so that you can use them effectively.

We have already completed the simplest work of the year, revising skills which you should be familiar with from previous years of mathematics – simple linear equations, systems of functions and basic coordinate geometry. Now, we start to go further, by investigating non-linear relationships – that means all lines that can be drawn on a graph that are not straight. The simplest of these are the quadratics – which have the shape of a smile (or a frown), just like the one in graph just above.

You will have studied this last year, and you may have become quite good at factorising and sketching quadratics – which is good. If you are not so confident, you will have time to revise, but you will have to put in additional work. We will be going a lot further with quadratics over the next month, and you will need to be prepared!

### Everything you wanted to know for the whole time about half-life in a quarter hour

February 20, 2013

So we are studying Atomic & Nuclear Physics – one of the most exciting areas of modern physics, and almost certainly one of the sciences that has most affected human history in the 20th century. It is one of the areas of physics that the public knows the least about, despite a great deal of interest. Even popular culture deals with nuclear power – from “The Simpsons” to “Battlestar Galactica”, from Iron Maiden’s Brighter than a Thousand Suns to Andy Warhols “Atomic Bomb”, every form of human expression from highest art to puerile comedy, from heavy metal to science fiction – the idea is everywhere.

I have written many posts on this blog about nuclear power (1, 2, 3, 4, 5) (you may want to pay particular attention to the comment streams…). Not only is nuclear power an important part of our studies, it is essential that all people who live in Australia are aware of the risks and rewards associated with nuclear energy, because like it or not, Australia has a nuclear future. I have written a specific set of class notes to supplement your textbook. You must download them, print them and bring them to class.

This post is specifically about the concept of half-life (no, not the game). Half life is the name given to the process of atomic decay, and particularly the rate at which particles undergo the decay process. Half life is an interesting process – and works very differently from other types of decay.

Take an example that is probably more familiar – fruit. If you have a bag of apples, what happens over time?