Archive for the ‘Physics’ category

Looking through medical imaging

September 18, 2013

Funny - Science - Physics - X-Ray shavingWell, 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).

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Physics is *powerful* stuff

July 31, 2013

Funny - Science - Physics - Cat Butter 2An’ Yur OUTTA here!

That’s Area of Study One, Unit Four, Down! Now it’s up to you to make sure it stays down for the count, and that you’ve knocked it out conclusively – time for some preparation, a bit of (mental) exercise before final round, the Assessment task.

Some mood music, Maestro, Please: Link

OK, back to the serious stuff. Each of you are working on a common resource to share for the summary of this area of study, but you must also be preparing your own summary sheet (one page, one side) to be used for this task, and then revised for the next and saved for the final examination. Those resources are to be ready for distribution via the Melba Physics page on Friday, so everyone has a chance to use them over the weekend.

The first assessment task is a straight forward test – we have a data analysis task to follow. You know the nature of the questions we discussed in class, but here is a link to the cover pages and formula sheet for the task. There are also links to files that we used in class here (1, 2). Make the most of them – they will help you prepare if you make sure that what you are doing is focused so that you ace this task.

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Physics is a *moving* science

July 21, 2013

funny - science - physics - kinematics - don't be a jerk

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).

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Motorin’ on!

July 10, 2013

To my year 12 physics class: Get to it!

More to come…

Ohm-o-Sapiens (evolved again!)

May 4, 2013

funny - science - physics - cruel circuit problem kirchoff lawThe 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.

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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:

1: Post on Circuit Analysis. 2: Updated list of youtube videos.

See you all in class!

Gravity Sucks!

April 5, 2013

gravity sucksThere is an unbearable pun about gravity. The fact that it is both a pun, and unbearable explains both why I know it, and why I would choose to inflict it on you. Of course, I won’t just say it, but imply that it exists – relying on the fact that right now, every bad pun about gravity is rolling through your head, and if not your fingers are twitching to Google whatever it is I am talking about – thus my purpose is achieved with minimal effort!

Regardless, the orbital movement is the final context of motion in two dimensions, our first area of study. It is clearly an outgrowth of circular motion, but it has some interesting twists of its own. For a start, the force that maintains the circular trajectory is the force of gravity – the first of the four forces of the standard model of physics. Gravity has some difference from other forces that you have thus far encountered. As an example, both Weight force (F = mg) and Elastic force (F = -kx) only involve the object that the force is affecting. Newton’s universal law of gravitation has some similarities to the weight force, but a great many more differences.

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

February 20, 2013

funny - science - physics - radiation mutationSo 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?

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Twistin’ and Turnin’ – Circular motion will set your brain a-burnin!

February 16, 2013

funny - science - physics - definitionSo. You’re back – you survived one year of physics, and you decided to come back for another. If you’re smart, you’re a bit scared! If you’re smarter, you’re already working your backside off and planning how you can work harder. This year we are starting with a review of 1-D kinematics from last year, and quickly moving into 2-D applications of the same ideas. The first one we are spending time on is circular motion – that is objects moving in a circle in either the vertical or horizontal plane.

Circular motion is hard to get your head around in the beginning, because your own experience is lying to you. Everyone has ridden in a car as it goes around a corner in the road or a roundabout – and you have felt the force “pushing you towards the outside of the curve”, so when you think about these forces, you have an immediate expectation that the force is acting outwards – from the centre of the circle out…

But you would be wrong!

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It’s rubber glove time!

October 14, 2012

STRETCH… SNAP.

It’s a horrible sound – the snap of a rubber glove. The implications of impending future are… not enjoyable. You are  about to have a physics exam which is the metaphorical equivalent of a rubber glove inspection for your brain. You’d better get ready!

The best way to prepare is to do enough questions. What is enough? Well, about twice as many as you think you should have done.

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