This Youtube Physics revision channel has started to take off. I’ve been lucky in that now is the GCSE exam revision time in the UK so lots of kids are surfing the web for revision material – There is a lot out there! So I am trying to find stuff that has either not been covered or something I can give my style to. I have stopped filming myself with tablet but I am now using an app called Explain Everything – it’s excellent and very easy to use. Also I am trying to keep my videos short as most videos seem to go on way too long – It’s difficult!
Here are a few examples of working with explain everything.
Do you remember those days at school when your physics teacher would tell you that the strength of gravitational acceleration is 9.8 m/s2? You just took it on blind faith that that was the strength of gravity right? Well, in the first of my Weekend Experiments series we are going to look at a very simple experiment anyone can do to find the strength of gravity in their local area (or planet). All we need is some string, a weight and your mobile phone to do some timings and a few calculations.
Myself and students of St Saviours High School, Leribe, Lesotho performing the Pendulum Investigation – 2010
What you need
A long piece of string – the longer the better
Somewhere to hang it from
A stop watch – just use the one on your phone
A weight – even a small stone will do
And a measuring tape or metre stick
Calculator – again use the one on your phone if desperate
What you do
Tie the weight to the end of the string and hang the piece of string up from the other end (remember the longer the string the better).
Measure the length of the string in metres to the nearest mm if you can.
Let the weight rest down and give it a little push – just a few cm will do.
The weight should now start moving back and forth in a pendulum motion.
Using your stopwatch we need to time how long the pendulum takes to go back and forth (We call this an oscillation). Human beings don’t have great reaction times so I suggest you time 10 swings or more in one go and find an average.
So here comes the maths – don’t freak out.
g = L4π2/T2
L is the length of your string in metres
π is that circle thing equal to 3.142 (approximately)
T is the time taken for one swing
L = 3.56m
T = 3.8 seconds
g = 3.56 x 4 x 3.142 x 3.142 / (3.8 x 3.8)
and I get..
g = 9.73m/s2
not a bad answer with just some basic equipment!
I HATE exams! I probably despise them even more than my students. They are probably the worst kind of assessment going and yet we rely on them so much. There is no situation in the employment world where you have to work individually and secretively, you’d be fired pretty quickly if you did! In the world of work you have to collaborate and be innovative, using key skills and knowledge to solve unique problems – how could we re-invent what is going on in the classroom to reflect this?
When it comes to revision time I have a flock of students around my desk asking for past papers. They know there is a chance that what has been covered in the past might well come up again, which of course it does. We run Cambridge international examinations here at my school and of all the exam boards I have worked with they do seem to push the key skills element of examinations and test if the student can apply the knowledge they have learnt to a different scenario but is this still enough? People have bad days, (I should know) and is it fair to test someone for one hour on about 200 hours’ worth of material? I don’t know if it but I can’t think of an alternative. I wish there was some kind of practical examination where the students get dropped in a room with some basic supplies and they have to use their physics knowledge to build a Rube Goldberg machine to get out! I guess the closest I’d ever seen to this is the physics game www.fantasticcontraption.com – which I strongly recommend. Can you imagine getting an IGCSE for your ability to play physics computer games, that’s the kind of syllabus I want!
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I’ve always loved taking things apart. I remember being about 6 years old and re-wiring the bike shed with wires swinging from overhead – luckily there was no electricity applied! Later in my teens I took apart my dad’s PC and unfortunately couldn’t remember the order in which I had dismantled it. I always remember that my dad didn’t seem to mind too much and in fact commented that he had done exactly the same with my grandmothers TV when he was younger. I guess tinkering has been in my blood since birth. Maybe be that’s where my love of Physics came from. With Physics you can take apart the universe and have a look at how it works, and so far without breaking it!
I’m very lucky that I have a job that I enjoy rather than endure. I’m not saying that teaching doesn’t come with its grinds, it can be frustrating at times but when you have all your students around you in the laboratory and you are demonstrating something exciting, the “oohs” and “arrrs” come out. You can see the students “getting it” and the light bulbs in their minds are switching on. It’s a very privileged position to be the first person to show someone how something works. I’m lucky that here in Africa I am teaching in a school that understands the importance of practical laboratory time. I have seen so many schools here that do not have a laboratory or even any real practical equipment. No simulation or reading from a textbook can beat actual tangible experience of experiments. An educational sales rep came to the school the other day to try to sell a 3D projector to us. She commented that “with this there would be no further use for the laboratory and that we would save so much money from not having to buy chemicals”. I love ICT in the classroom, it saves me a whole lot of time but replacing experiments it will never do!