Look out! It’s Newton I!

You know you’re a physics geek when the first thought that comes in to your head when watching all those car crashes on the news is: Now that’s what I call Newton’s first law of motion!

First law:
Every body remains in a state of rest or uniform motion (constant velocity) unless it is acted upon by an external unbalanced force.

Now most people think that this force simply slows the car down, but in the world of physics the word velocity covers two quantities; speed and direction. So it could be that the force merely changes the direction of the moving object, and has (little or) no effect on its speed. In fact that is what is happening when an object is moving in a circle (like a stone tied to the end of a rope circling over your head; the stone is moving at constant speed yet we still say that it is accelerating because its direction is changing). In this case the force is provided by the tension in the rope acting inwards.

We demonstrate this in class with an air-track, which is a bit like an elongated air-hockey table. A nice way to re-inforce the concept is to discuss why, when moon-bound rockets leave our gravitational field they can turn off their propulsion system and will remain moving at that speed untill they reach the moon’s gravitational field (although technically both gravitational fields are infinite – but that’s for another day).
Galileo himself (for it was he and not Newton who first promoted this) had great difficulty persuading others of the importance of this discovery.
The response of the students to the air-track demo is a reminder of how strange this idealised world of no friction actually is to us.

But every now and again we get to experience it for ourselves.

Junior Cert Physics Investigation 2010/2011

The junior cert science investigations for 2011 were published recently and the phyiscs investigation is as folows:

Investigate the factors that determine the force of friction between a  wooden block and the surface on which it is resting.

As usual,  there are few spaces for science teachers to discuss how best to implement this investigation so for what it’s worth I’ve decided to throw out my thrupenny worth of ideas and resources.
Why should my students have an advantage over other students who perhaps have a biology specialist as their teacher? Hopefully a Biology/Chemistry teacher will reciprocate with their comments on the other investigations.

Alternatively maybe a student will happen upon this blog post as part of their research – if so good luck to you. Please let us know how you’re getting on and we will try to help.

Some points to consider:

  • You would imagine that the orientation of the block would make a difference: if the block is standing on edge then there is less surface-area and presumably less friction. But presumably isn’t good enough in physics; many (maybe even most) relationshiops in physics which were originally thought to be obvious turn out after suitable investigation to be actually wrong. Can you think of any?
    To see a demonstration of this see the link here (pull the tab at the bottom over to the 10 minute mark – thanks to colleague Dee Maguire for the link and the heads up on the approach above).

 

  • There is a another nice counterintuitive concept – if students  are playing with different types of sandpaper they may well find that  the friction force between the wooden block and the roughest type of sandpaper is actually less than the force of friction between the wooden block and the lab-bench.
    Hopefully the students will first notice this stange relationship and then figure out why for themselves (this should then form part of their report. Partial explanation – the grains in the very rough sandpaper are acutally acting like little ball-bearings (see link below for an animation).

 

  1. Friction between two rough surfaces from absorblearning.com
  2. Friction between two rough surfaces
  3. The effect of ball-bearings in reducing friction
  4. The effect of lubrication in reducing friction
  5. Rub the two books against each other and note the rise in temperature

The origin of the decibel scale

A standard leaving cert physics exam question is “why do we have the decibel scale”?
The standard answer is that the range of sound intensities is so large that a second, much more compact scale is required to make the numbers more manageable, and for sound this scale is based on multiples of ten and is called the decibel scale (and what it measures is called sound intensity levels).

The old syllabus included a detailed analysis of this scale so that the numbers actually meant something. For the new syllabus (2002 onwards) it must have been decided that the maths was too difficult so this part was scrapped, except for one very odd ‘fact’; the student must know that a doubling of the sound intensity results in an increase of sound intensity level of  3 dB. Now needing to know that piece of useless trivia is ridiculous and is probably only there as a sop to some university professor who was horrified that the detailed analysis was dropped:

At least that’s my best guess, which doesn’t seem too dissimilar to what the author of a recent book on Physics and Music  entitled How Music Works thinks about the decibel in general.

I think the decibel was invented in a bar, late one night, by a committee of drunken electrical engineers who wanted to take revenge on the world for their total lack of dancing partners.

Ouch!

How Music Works: The Science and Psychology of Beautiful Sounds, from Beethoven to the Beatles and Beyond
by John Powell

Now what’s the betting that students will remember this explanation and forget all about the technical one?

Harry Chapin – Flowers are red

Criticising our education system is not new – why would it be when it’s like shooting fish in a barrel? One of the better known recent commentaries came from Sir Ken Robinson at a TED conference a few years back who made a very convincing argument for changing our focus away from the  academic subjects and instead develop a greater emphasis on the arts as part of our students’ formal education.

Sometimes the best critiques come not from ‘experts’ but from those well outside the academic circle. Harry Chapin’s Flowers are red  always been one of my favourite songs in this regard. It really doesn’t require anything more to be said. Listen for yourselves and if you’re a science teacher ask yourself which teacher you want to be like.
And then try to answer honestly which of the  two teachers your students would match you with.

Remember almost every student comes into secondary school with a deep sense of wonder which is all you should need to succeed in Science. Few leave with this passion still in good working order. We must at least allow for the possibility that we teachers are part of the problem.

Aims and Objectives won’t get us out of this one.

An Engineer’s Guide to Cats

For many years now many of my brightest and best students have gone on to study Engineering, despite my best efforts to the contrary.
I consider an engineer to be a physicist who has lost his sense of wonder.

By the way, do you know where the term ‘civil engineer’ comes from?
Apparently it was to distinguish engineers who worked outside the military from those who worked inside it.
Thanks to The Guardian for the heads up on the video.

Benoit Mandlebrot and The Colours of Infinity

The Colours of Infinity is a wonderful title for any documentary so it is only right and proper that  the program itself lives up to the title.

I show parts of  it to Transition Years in an attempt to stimulate a sense of wonder for Mathematics. It by no means manages to undo the damage caused by their maths education up to this point, but it may just mitigate it somewhat. I have shown excerpts of it in the last couple of days to most of my students in all years, not because it’s Maths Week (or was that the week before?) but because the central character, a man by the name of Benoit Mandlebrot, died last Thursday. In each class the assigned homework was merely to go onto YouTube and watch as much of the rest of it as they could get away with.

I won’t try to explain what it’s about; what would be the point? By this stage you are either a fan of my recommendations or you’ve given up reading them. Either is cool. But if there’s only one extra-curricular maths program you ever watch in your life, make it this one.

Come to think of it, it should be mandatory for all Art students to watch it also; just one more example of the cross-over so beloved of our school inspectors.
Finally, if you have an iphone why not download some of the incredible images associated with fractals? Just do a search for ‘fractals’ in the app store.
In fact when entering the title into YouTube, the images alone from the page it brought up should be enough to entice you in.

Please put SPACE on our Science syllabus

science.ie is currently hosting a survey of readers to find out what they consider to be the greatest mystery in Science. The leader by quite some way is “How did the universe begin?”

The theme for this year’s Science Week is “Our place in space“, and no doubt thousands of students will spend an hour or two attending special lectures which highlight this wonderful concept.

Then we all go back to our classrooms and never again hear about space, never mind the Big Bang.

If we want to grab students and hold onto them then while ScienceWeek is a nice resource, it is certainly not the answer. Why are we not telling students about the Big Bang, Quasars, Neutron Stars, Pulsars, Black Holes and all manner of other exotic phenomena as part of their science education? Because it’s not on either the Junior Science or Leaving Cert Physics syllabus (although the Big Bang does make an appearance in the Leaving Cert Religion syllabus).
And it’s never going to be on these syllabi unless we kick up a fuss. For that to happen there would first need to be a recognition of the problem. Why can’t Chris Horn and all those other commentators from the business world take an hour or two to look at our syllabi and then ask themselves – ‘would I want to study this for either three or six years?’

I don’t know if other teachers feel the same because there is so little communication between us, but that bone of contention is for another day.

This is just to serve as advance notice – next time you hear an ‘expert’ on the national airwaves bemoaning the low numbers of students taking up Physics or Chemistry, listen our to see if there is any evidence to indicate that the speaker is actually familiar with either syllabus. And listen very carefully for the one word that never gets mentioned by these business folk: wonder.

Is it a particle or is it a wave?
Sometimes I think I’d gladly be locked up in a dungeon ten fathoms below ground, if in return I could find out one thing: What is light?
Galileo, from the play Life of Galileo, by Bertolt Brecht

 The single greatest source of debate among physicists in the early decades of the last century was to do with the nature of light. Come to think of it, this concept has probably caused more angst than any other to scientists and philosophers right back to the ancient Greeks.
To take just one aspect; we can prove that light is a particle (via the photoelectric effect) and we can prove that light is a wave (via interference, or the famous ‘double slit’ experiment) yet particles and waves are two completely different phenomena. Particles are ‘things’ and are therefore supposed to be localised in space and have mass. And while there are  different varieties of waves, they are not supposed to be ‘in one place’ or have mass.
So what gives?


 

Answer: nobody knows. To this day there are different interpretations, but none that is accepted by all. The YouTube clip below shows some of the world’s greatest physicists coming together for one of a series of conferences to try to make sense of it all back in the 1920’s. Needless to say they did not reach a consensus. There is wonderful book called QUANTUM which describes in great detail the history of this debate at the beginning of the last century. See here  for a previous post on the book itself.

Now in leaving cert physics we need to know the evidence for light being both a particle and a wave. But there is room in the syllabus or any of the textbooks that I have come across to highlight the bizarre nature of this. It lies at the heart of one of the greatest problems scientists have ever faced, and our response is to simply pretend that there is nothing of note here.

It’s simply not good enough.

Science and Religion with Mr. Diety

Pretty much self-explanatory.
This one is about the somewhat tricky concept of how to create both matter and time.

Mind you I’m not sure Science is doing much better at an explanation, but we tend to hide that little fact behind a barrage of highly technical and long-winded sentences so it’s not so obvious.

And then there’s the wonderful Michael Shermer – skeptic extraordinaire – appearing rather sheepish when he realises that backed the wrong horse:

Check out the related videos on the side panel.

And now for something completely different:

A big welcome to morestresslesssuccess

 

As teachers, most of us are happy to spend hours giving out about all that’s wrong with our education system and what should change. All too few of us however are prepared to put our head above the parapet and take the time to make our opinions public (with the obvious exception of salary talks). It doesn’t help that the main teacher organisations are reluctant to set up discussion forums – possibly for fear of legal repercussions should the wrong thing be said.

Which is why we are delighted to welcome morestresslesssuccess  to the blogosphere. The blogger in question is Humphrey Jones (pictured above) of thefrogblog fame. It’s best described by himself:

More Stress, Less Success is a blog about being a teacher – a busy one. But more specifically it is about recognising the work that teachers do in a society where they are rarely valued. It’s also about exploring new ways to teach and learn, specifically using technology.

 I don’t know if I would say that teachers are rarely valued – personally I believe that as a profession we could be doing so much better and so much more to help ourselves (and yes of course I include myself in that). Our teaching styles (at secondary level at least) are still very much ‘chalk and talk’ together with ‘the sage on the stage’ when that whole approach has been lambasted by educationalists for decades if not centuries.

Nevertheless it’s great to have the opportunity to ‘converse’ with a fellow teacher in this fashion – I suspect we have a lot more in common than not, and I luck forward to changing my own opinion when needbe.

With a bit of luck it may just prompt some more ‘lurkers’ out into the open.