leaving cert physics

My contribution to Science Week – I thought I might teach some physics

At 40 mins long it’s not going to go viral anytime soon. It’s the middle 40 minutes of a double class but in it we managed to learn about some of the following:

The structure of the atom.

We, and everything around us, are mostly empty space.

We discovered that the appearance of  ‘solidness’ is an illusion – which lead to a  discussion about how light works.
We learned that there is a cultural aspect to what we see (and you definitely won’t find that in physics textbooks) and that Newton himself was subject to this and it resulted in him making a boo-boo that still goes uncorrected right up to today.

We discovered that electrons are constantly cascading down along everything we see in a seemingly never-ending avalanche, powered by energy from incoming light (so when this power source disappears, the electrons no longer have energy to jump up or fall back down, otherwise known as darkness).

We learned why things feel solid – all to do with the force of repulsion between electrons at the surface.

We developed a deeper understanding of Newton’s Third Law.

We discussed the fallacy of language – know the word for something (like gravity) and understanding what gravity actually is are two very different things, and shouldn’t be confused with each other.

We discovered that physics teachers don’t have all the answers, and should never pretend otherwise.

We were reminded that because almost none of the above is in the syllabus, the syllabus is a disgrace. It’s no wonder students don’t see the point of it.
There were 22 students in that class and the discussion could have gone on and on – I had to kick them out the door.  One can only imagine the conversations they must have had over the dinner table that evening.

If only all those who make such a fuss over Science Week could put a fraction of that effort into making the school syllabus a source of wonder and curiosity instead of what it is – a series of dull as dishwater facts which are to be merely learned off by heart.


How to Get 100% in Your Leaving Cert Physics Exam (Without Really Trying)

I am not happy with the Leaving Cert Physics exam. In a nutshell – it’s too hard. The vast majority of the questions come from material teachers cover in sixth year, and the closer you get to the end of the course, the more popular the exam questions. Nothing wrong with this so far, except when you consider that this often represents the most difficult sections of the course. And never forget that Physics is a difficult subject to come to terms with at the best of times. So many concepts are very, very counter-intuitive. After all, only one civilisation ever accepted it as a means of generating knowledge about the world around us.

Even if you look at some of the material that we do cover in fifth year, the questions on this in recent years have been very, very difficult. Optics is usually the first thing we cover and yet, based on the questions on this topic that appeared in 2011 12 (b) and 2012 12 (b), I now have A students who swear they won’t go near the topic if they see it on the paper this June.

Which is why the following document seems is very popular with students (particularly those struggling a little with the subject).
It looks at the pattern of questions that have appeared since the syllabus first came into existence in 2002 and allows you to decide what questions to focus on.

For example Static Electricity and Capacitance are two short chapters, and they have appeared every year since 2002 as a half question, with the exception of last year, so expect them to make an appearance this year.

Electromagnetic Induction came up every year from 2002 to 2008 as either a full or a half-question. It hasn’t appeared since 2008 however. Expect it to appear as either a half or a full question.

The Electron has appeared on 9 of the last 11 years. Nuclear Physics (that’s Radioactivity and the atom, along with Fission, Fusion and Nuclear Energy) has appeared every year as either a half or a full question.

You can see similar patterns for other topics listed in the document. The important point is that, assuming you’re going to do Question 5 (series of short questions which cover the entire course, with choice built in) and Question 10 (Particle Physics; comes up every year) then you really just need 3 questions from the remaining 6 (and one of these is Question 12, which offers a choice of 2 parts from 4).

Every year since 2002 you would have been able to answer a full paper by just learning the topics below (and usually with some choice to spare).

You still need to cover all Mandatory Experiments for Section A, and all definitions for Question 5, but if you’re a D or C student it would be highly advisable to use this as your guide. If you’re looking for the A then you really need to cover all topics on the course to cover yourself for all eventualities.

You can access the document using the direct link here or, for future reference, in the revision page of thephysicsteacher.ie

The g-ball: a nice alternative to the traditional experiment

Setting up the apparatus for the Leaving Cert Physics experiment “Measurement of acceleration due to gravity using the method of freefall” can be tricky at best.
I recently ordered something called a ‘g-ball’ from ibotz for about €40 which does much the same thing. And at that price you could probably get a few of them and have different groups doing it separately.

The link below is a video of the g-ball in action.

There are all sort of errors involved, but it’s still reasonably accurate and errors can often serve to act as source of further discussion.

I like it in that it takes away all the confusion associated with the traditional circuit which I think distracts from the important physics (drop a ball; measure time of fall and distance traveled and from this work out g using a very simple equation).

If I was setting up a lab and trying to save money I would use the g-ball instead of the traditional set-up (while still ‘learning’ the traditional set-up for exam purposes).

To order the g-ball contact the boys at ibotz.com
Oh. And did I mention that it’s fun?
Physics? Fun? Who’d a thunk?

By the way, this is the traditional method:

An appreciation . . .

Every now and again I get a letter like the following, which makes all the time and effort put in over the years worthwhile. The letter has been edited slightly to protect the innocent.

(I also just received my first donation on the website – thanks Lisa – so I’m now up to a grand total of €50.  Actually my sister also donated €1 over a year ago, just to confirm that the link was actually working, but I’ve been meaning to give that back).

Dear Sir,

My name is ______________.  I am a student who undertook Physics for Leaving Cert 2 years ago.
My physics teacher . . .
I was under the impression that Physics would be an easy subject . . . and that it required no work. How very wrong I was.

When I saw notes over the summer of 5th year belonging to my friends in other schools I saw how much work I had to do. Luckily I stumbled across your website and from then on things looked brighter. I suggested the site to my class mates and we immediately started to ‘get the hang’ of Physics.

I scored an A2 in Physics and surpassed my expectations. Of a class of 18 there were 3 A grade, 12 B grades 2 C grades and an A at ordinary level, all thanks to you and your marvelous notes.

I’ve gone on to study Biomedical Science. I still use the basic fundamentals of physics everyday, and I learned these fundamentals from you. 4 from the class went on to study Physics in the class, 6 went on to do Engineering, and 2 are studying music. The rest are in Mathematical Sciences and Veterinary.

On behalf of our class, I just wanted to thank you. We may never meet you in person, but you have made a huge impact on the direction of our education, simply by making what we were learning interesting. I cannot thank you enough for this.

My sincerest thanks and best wishes,

Leaving Cert Physics exam – final advice

Looking for a top grade?

Just one day to go.

Wondering what topics to concentrate on?

Consider the following:

Electromagnetic Induction has appeared on past exam papers on the following years:

2011 —

2010 —

2009 —

2008 no.8

2007 12 (c)

2006 no.11 {5/8 of a long question}

2005 12 (b)

2004 12 (c)

2003 12 (d)

2002 12 (c)

That’s right – it’s appeared every year from 2002 to 2008 but not for the last 3 years – don’t go into the exam without knowing it back to front and upside down. The document which contains all past questions on this topic together with the worked solutions can be found on the revision page of thephysicsteacher.ie.

How about The Electron?
Let’s take a look:

2011 —

2010 no.9

2009 no.8

2008 no.11{5/8 of a long question}

2007 —

2006 12 (d)

2005 12 (d)

2004 no.9

2003 no.9

2002 no.9

So most years it’s a full question, but hasn’t appeared last year at all. Same advice therefore – see all questions and solutions on the revision page of the website.

Particle Physics comes up every year – this year was the 75th anniversary of the Cockroft and Walton experiment – pay particular attention to past questions on this topic.

In fact for a full overview of all questions likely to appear this year (tomorrow!) you could do worse than check out the following:

If you want to download this document then the link is here

And remember – expect the unexpected. If something comes up that you haven’t seen before then just deal with it. Welcome to the real world!

And good luck with it 🙂

The nature of matter

Few concepts in Physics generate wonder quite like Quantum Theory. You only need to look at the shelves in the Popular Science section of a bookstore for evidence. Yet (once again) in schools we play down this sense of wonder. I used to think this wasn’t done deliberately but now I’m beginning to learn that there was once a school of thought that believed in doing exactly that, particularly for Science (more on that later).

Anyways, one of the most incredible ideas in Quantum Theory concerns the nature of matter itself – is it a particle or is it a wave?
For light, we can prove that it’s both (ridiculous though that may sound) and indeed students are expected to know the demonstrations which verify both. There is however no suggestion anywhere in either the textbooks (that I have come across) or in the syllabus that there is anything slightly disturbing in this. There was a single question on the exam paper once which asked why was Quantum Theory considered revolutionary, but that was it. No other reference to what is one of the greatest mysteries of science; how can something be both a particle and a wave. Why do I seem to be the only one who feels so frustrated by this?

So in an attempt to pass on some of this sense of wonder for the microscopic world, I put together the following set of demonstrations for my sixth years on the last day of term. It’s about 22 minutes long so is in two parts. Forgive its amateur appearance.

How to get 100% in your leaving cert Physics exam. Part 3: Short Questions

Question 5 on the paper is 56 marks and counts for 14% of the overall mark. The choice is to do 8 questions out of 10. It is one of the more popular questions on the paper.

I have compiled a list of all the short questions which have been asked over the last ten years,  together with their solutions. It is a detailed document (26 pages) but is worth knowing not only because it prepares you for Question 5, but also because it provides a comprehensive overview of all the topics on the course itself.
I have included the years with the questions because it helps to identify the questions which are particularly popular with the examiners.

State The Principle of Conservation of Momentum.
[2002][2009 OL][2008 OL][2007 OL][2005 OL][2004 OL]
In any interaction between two objects, the total momentum before the interaction is equal to the total momentum after the collision, provided no external forces act.

And to my mind the two most popular questions at higher level:

What is the Doppler effect?
[2008] [2007] [2006] [2003] [2002]
The Doppler Effect is the apparent change in frequency due to relative motion between source and observer.

Define electric field strength.
[2009][2007] [2005] [2003] [2002]
Electric field strength is defined as force per unit charge.

There are a lot there so don’t try to learn them all at once; take a couple of pages each day, but then make sure you keep going over them (from the beginning each time) and in no time you’re confidence will be sky high!

Try to print two pages onto one sheet, and also back to back if possible to save paper.

We are empty space

Having to pick out the singular most incredible concept in physics would be an interesting task (to say the least). Rarely a day goes by without me invoking the term ‘awesome’ in some context or other. I really do have a wonderful job.

Today however I came to what I think may be my favourite – the structure of the atom. You see the concept of solidity is merely an illusion. That table appears to be solid but actually it is 99.9999999% empty space.

“But it looks solid!”
Yup – but that’s (just) an optical illlusion caused by the interaction of electrons and incoming electromagnetic radiation.

“But it feels solid – when I bang my hand off the table I feel a solid surface!”
Again an illusion I’m afraid. This time caused by the interaction between electrons in your hand and electrons on the surface of the table repelling each other.

So next time you’re sitting in your car holding on to the steering wheel, just remind yourself that the steering wheel is hardly even there – neither is the car and for that matter neither are you (I’m trying not to have an exclamation mark at the end of every sentence here, but it’s not easy).

Now there is a (very, very) small amout of ‘matter’ in you. And here’s the thing; if you somehow managed to remove all the empty space in your body you would be left with a lump of solid matter which would be smaller in size than a grain of salt. How much would it weigh you ask? Why the very same as you do now, after all we have only removed the empty space (having a real tussle with the exclamation mark key here).

Okay, but this is all theoretical right?
Well maybe. It’s theoretical for humans, but there are objects out there which do not have empty space in them and which therefore are incredibly dense. They’re called neutron stars and to quote from Wikipedia:

this density is approximately equivalent to the mass of the entire human population compressed to the size of a sugar cube.

This gives them some other unusual properties. The radius of a typical neutron star is about 12 km, and just like a pirouetting ice-skater whose rate of rotation increases as they draw their arms in, so also does the rotation of a neutron star increase as its radius decreases. So how long does a full rotation last (remember that on Earth this is 24 hours)? On average there are somewhere between 100 and 1000 full rotations per second (see, if I can’t use exclamation marks at least I can use italics).

But back to the atom. To help students appreciate that it’s not just me who is bonkers, here I invoke the assistance of some more well-renowned experts.

Professon Brian Cox

Note that it took Rutherford two years to arrive at a correct interpretation of these results. It’s not like what you see in the textbooks – describe the experiment and then form an obvious conclusion.

It kinda freaked him out – Neil de Grass Tyson (audio link)

And for a bunch of other links see the related page on my website.

And finally, while you are expected to know that the atom is mostly empty (and be familiar with the experiment that ‘proved’ it), there is no sense in either the syllabus or any textbook I have come across of the wonder associated with this crazy idea. In fact it’s normally presented as just another piece of information to be learned off my heart. And I never hear anybody giving out about this, so I save my rants for unfortunate students and the odd blog post like this.

Now that’s mad!!