leaving cert physics

What do lightning conductors and Global Warming have in common?

Recently when covering Static Electricity we looked at how lightning conductors work, but we also discussed why they took so long to catch on.

Try answering the following questions without looking at the answers (I know you’re not actually going to do this, but it gives you a sense how the conversation went in class).

Me: Give me some examples of what you can NOT insure your house against.
Students: Floods, hurricanes, earthquakes

Me: What are these collectively known as?
Students: Acts of God

Me: Why are they referred to as Acts of God?
Students: Because you can’t predict when or if they’re going to happen.

Me: But why would you call those events ‘Acts of God’?
Students: Because you can’t predict when or if they’re going to happen.

Repeat three times.

Me: But why would you call those things ‘Acts of God’?
Student: Because God must have wanted those things to happen – or at least that’s what the people believed back then.

Me: Exactly. And before you all laugh at how ridiculous that sounds remember that it’s not that they were any less intelligent than we are now, it’s just that life in the 16th and 17th century was incomparably different to today. We live in a so-called age of reason. We know you can’t say ‘well that’s obviously what God wanted’ every time something bad happens. And I’m pretty sure that if our civilisation survives another century or two the people who are around then will look back at some of the rather bizarre belief systems that we subscribe to. The United States contains approximately 5% of the world’s population yet in incarcerates 25% of the world’s prison population. Enlightened?

Even Newton himself fell into this way of thinking. When he found out that the orbits of the planets didn’t quite match his mathematical equations his response was to say that God obviously needs to step in and give them a nudge every so often. It took Einstein to explain that the problem was that Newton’s equations weren’t exact enough and it needed his (Einstein’s) Theory of Relativity to sort out the anomaly.

The point is that, as with so much of the Church’s teachings, its beliefs can be traced back to either St. Augustine or St. Thomas Aquinas. In this case both believed that the air was filled with seriously questionable characters. Aquinas wrote that “Rain and winds, and whatsoever occurs by local impulse alone, can be caused by demons. It is a dogma of faith that the demons can produce winds, storms, and rain of fire from heaven.”
And so, presumably, can God.

So when Franklin suggested that his lightning rod could save  church buildings he naturally thought that this would be well received (in fact he considered it to be one of his greatest accomplishments, which is no mean feat when one considers that he was also one of the founding fathers of the United States.) It turns out that his suggestion went down like the proverbial lead balloon.

If a building struck by lightning was an Act of God, then interfering with this process was akin to thwarting God’s plan. And that, in the eyes of the Church authorities at least, couldn’t be a good thing. So they simply refused to put them in.

But there was one small problem. The church building was invariably the tallest structure in every village and town. So it was also the most likely to get hit. Now as you can imagine this confused people greatly. Not only that but the bell-ringers whose job it was to alert the townsfolk about the impending storm also tended to become the first victims of any lightning strike. In Germany alone approximately 300 bell-ringers lost their lives in the last 30 years of the 19th century.

So slowly but surely Church authorities began to relent and accept that maybe it was time to accept that there was something to be said for these so-called ‘blasphemous devices’ after all. Lucky for them it wasn’t too late.

So what’s all this got to do with Global Warming?
According to one 2006 study, 76 percent of Republican citizens profess a belief in the Second Coming (the so-called ‘Apocalypse’). They also represent one of the largest groups who oppose scientific teaching on Global Warming. They simply refuse to accept that Global Warming has the potential to change the world irrevocably. Why? Because the end of the world will come at a time of God’s choosing, not ours, so whatever mankind is doing right now, it’s certainly not going to bring about the destruction of civilisation.

These religious conservatives have become a very powerful force in American politics in recent decades (how that came to be is an equally fascinating story, but not for today).

Add to this the lobby group for oil and other fossil fuels and you have a voice that is both loud and very difficult to dislodge.

Now for fun throw in optimism bias which is evolutionary hardwired into all of us. Optimism Bias is the belief that the future will be better than the past. So for example 10% of Americans expect to live to be 100 when in fact only 0.02% are likely to live that long.We all experience optimism bias. It’s why none of us mention Global Warming when political canvassers call to our door. We all just assume that it will get sorted somehow. It may even explain why we are all so reluctant to engage with the concept of our own mortality; deep down we all think we’re going to live forever.

So you can see why Global Warming remains low on everybody’s radar.

And it will most likely remain that way – until it’s too late.

Unlike lightning conductors.

This is a link to resources I use when teaching about Global Warming and The Apocalypse in Transition Year.


Just so you know, nobody knows what energy is

The following acts as my introduction to the students’ notes on the Energy chapter.

What is energy?

Nobody knows what energy actually is and by pretending otherwise we actually do you the student a disservice. Not only are we ignoring the wonder associated with the idea, we are also denying you the opportunity to engage with the concept at any level beyond the superficial.

Bottom line; nobody gets energy because there’s nothing to get. Energy is not tangible (it is ‘an indirectly observed quantity’); you can’t hold it in your hand, you can’t weigh it on an electronic balance, you can’t see it, touch it, smell it etc. Yet when the universe was first created there was a certain amount of this put in to the mix (actually now that I think about it the mix itself was energy (with perhaps just a little dash of time)), and it’s all still there today. Its form can change, but the energy itself can’t ever disappear – no sirree bob.

It could be argued that it is in fact merely an accountant’s trick which enables him to ensure that all actions balance.

Consider the following analogy which I like to use.

If a child asks you ‘what is money?’ you could take a few coins out of your pocket and show them to the child and say ‘this in money’. Now fast forward a couple of decades; all transactions are now done electronically/online and all coins and paper money are no longer legal tender. Now how do you explain what money is?

Well it’s a means of payment for goods and services, right? Somebody sells you an orange and you agree to transfer into their account a set amount of this ‘money’. And now that the shopkeeper has this money in his account he can use it to buy something else. So in effect money is just a transferrable IOU.

Now energy is a bit like this, but there is only a certain amount of IOU’s in the universe and this was set when the universe first came into being.

To complicate matters further, since the early part of the last century we now know (thank you Albert) that all matter (‘stuff’) is basically energy in another form.

Anyone still with me?


All right, let’s listen to Richard Feynman give his take on it.

There is a fact, or if you wish, a law governing all natural phenomena that are known to date. There is no known exception to this law – it is exact so far as we know. The law is called the conservation of energy. It states that there is a certain quantity, which we call “energy,” that does not change in the manifold changes that nature undergoes. That is a most abstract idea, because it is a mathematical principle; it says there is a numerical quantity which does not change when something happens . . . it is a strange fact that when we calculate some number and when we finish watching nature go through her tricks and calculate the number again, it is the same. It is important to realize that in physics today, we have no knowledge of what energy “is.” We do not have a picture that energy comes in little blobs of a definite amount. It is not that way. It . . . does not tell us the mechanism or the reason for the various formulas.

The Feynman Lectures on Physics Vol I, p 4-1

When Feynman wrote,
“It is important to realize that in physics today, we have no knowledge of what energy is,” he was recognizing that although we have expressions for various forms of energy (kinetic, heat, electrical, light, sound etc) we seem to have no idea of what the all-encompassing notion of “energy” is.

The various forms of energy (½mv2, mgh, ½kx2, qV,mcT, ½I2, ½CV2, etc.) are abstractions not directly observable.

2007 American Association of Physics Teachers

Now with that interesting bit out of the way, let’s go see what we need to know for the exam.


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

International Particle Physics Masterclass n UCD for 5th & 6th year Leaving Cert Students

I received the following from UCD and thought that the best way of getting the information out was to post it here.It certainly looks like something you should follow up on if you are thinking of taking Physics in college or, as they mention here, have a keen interest in computing:

Dear 5th & 6th Year Teachers and Students (Science/Physics),

UCD School of Physics is delighted to accept applications for our 2nd International Particle Physics Masterclass (IPPM), aimed at 5th & 6th year Leaving Certificate Secondary Students.

This is your chance to get your hands on real LHC data and analyse it to find W & Z bosons, and look for evidence of the Higgs!

UCD School of Physics as part of a worldwide initiative is inviting students from around Ireland to participate in a one day Masterclass to delve deeper into the mysteries of particle physics.

Last year’s IPPM event was a great success with students from 35 schools nationwide coming to UCD Physics for a day of hands-on-learning about particle physics. This year again we invite you to apply for a place on the UCD School of Physics International Particle Physics Masterclass 2013.

UCD School of Physics, will provide students with state-of-the-art computing facilities, specialised software, expert guidance and real data direct from the CMS experiment at CERN in order to allow you to look for W & Z bosons produced in the collision of two protons at the LHC.

This activity is open to 5th and 6th year Leaving Certificate students, with a keen interest in Physics. No advanced experience (beyond studying
physics or maths for Leaving Certificate or a keen interest in computing) is required, though an interest in particle physics and the
recent results from CERN is an advantage. This is an excellent opportunity for students who are considering entering a Physics focused
third level education path.

The UCD School of Physics International Masterclass 2013 will be held on the 20th of March. The activities will start at 9:30am and finish at
4:00pm. The day will consist of practical lectures, hands-on data analysis, and an international video conference to compare your results live with students in other countries. (If you can’t make it on the 20th March, similar activities will be running at Maynooth NUI on March 6th and Trinity College Dublin on February 26th.)

Click on the following link for the UCD IPPM Application form in .doc (MS Word) format.

If you or members of your physics class at school would like to participate at the UCD School of Physics Particle Physics Masterclass, please ask your teacher to send an email to the appropriate address (email address is available in the MS Word document) with the subject line ‘PARTICLE PHYSICS MASTERCLASS’ (or fax 01-2837275).
The closing date for receipt of applications is Wednesday, the 6th March, 2013.
Successful applicants will be contacted in early March.
This event is free of charge.

Further information at:

http://www.ucd.ie/physics/ppmasterclass/ [2] and
http://www.physicsmasterclasses.org/ [3]

Addition of vectors

What happens when, if travelling forward at 100 km/hr, you throw something backwards at 100 km/hr?
It may be tricky to demonstrate in class, so here are a couple of useful resources.

From a Japanese TV show – a real life example of adding vectors and relative motion. Scroll forward to the 3 min mark if this doesn’t happen automatically.

Then Mythbusters wanted to try it

Can you explain why?

Isn’t Physics just mad Ted?

Now for something completely different (well there are some references to direction in there, so it just about qualifies).

Links to each of these resources are available on the Vectors page of thephysicsteacher.ie

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.