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!
What should you do when parents have unrealistic expectations of their children? Recently at school the students received their IGCSE and AS level results. There was very large crowd outside of the principal’s office, crammed full even, with lots of expectant children and parents. Many of the students were being congratulated as they received their certificates and one of the girls fainted when she got her results. One parent asked me if I thought their child would get an A or B for their AS level but as that student only got a C grade at IGCSE, the level of expectation was simply way too high. It is always difficult to know what to tell a parent when they simply have too much expectation of what their son or daughter is capable of but the simple fact is students generally do not do better at AS level than IGCSE because the subject level is so much harder.
Recently I went to my own daughters parents evening. She has just started grade R. Some of the parents in the meeting wanted to know how quickly their child could be moved into grade 1. The principal quite rightly responded that with differentiation in the classroom that student would still be pushed and it is not necessarily wise to jump up a grade. One of the parents would not give up and was convinced that their little darling was a genius. The honest truth is that most children are just average at most things and with time develop specialist skills with positive feedback from parents and teachers playing an important guiding role. What’s the rush to get a child through high school? School is not just about grades and academics, perhaps more importantly it’s about social interaction, making friends, understanding how to interact with other people. Children should always be encouraged and supported throughout their education but over-expectation is dangerous, puts stress and pressure on the child and must be avoided at all costs.
I don’t know where I got this interest in QR codes from as they are not that popular yet in South Africa. On recent trip to the UK I found them often in newspapers linking to product websites and wondered how difficult would it be to make my own. A lot of students now have phones capable of reading QR codes so I thought it would be a fun to make a QR code treasure hunt. I decided to only inform the principal of the school and no member of staff to keep it as secret as possible. The interesting thing about QR codes is the it’s not like a normal treasure hunt as there is an air of mystery about these unusual symbols. You don’t tend to notice QR codes as much as normal text and it was a lot of fun hiding them around the school. We had eight base stations in total and I designed the clues so that it wouldn’t matter which QR code the students scanned in first with a loop of 8 different clues. With each clue the students would gain an extra letter and these letters would all make up a master key word. One of my favourite hiding places for hiding the QR codes was behind one of the basketball hoops. If you are interested in making your own QR codes there are plenty of apps and also many free online QR code generators.www.the-qrcode-generator.com/ was the website that I used to make my QR codes as it outputs the QR codes as simple png format that can easily be printed
So much of a teacher’s time is spent on struggling students who do not understand concepts. I would estimate that 80% of my time spent with students is trying to guide the students who are failing and I generally leave the students who are working well to just get on with it. Of course there should always be differentiation going on in the classroom but gifted and talented students simply do not get their fair share of my time. How could I change this? I’ve been looking at Flip Teaching, The process where you record your lessons on a tablet and the students watch the video back at their own pace, answering questions as they do. I tried using the principal’s iPad to record a basic test of the idea using an App called show me. The great thing about show me is that all the recording and publishing software is built into the app. The only problem I have with it is that all the material that you produce goes straight on to the show me servers and I have no control over it. Here in South Africa we are still limited by our broadband speed so it would be much more useful to dump the videos on the local server here in the school than have them eating away at our bandwidth and data usage, which at R30 per gigabyte can soon get expensive when 30 students are all streaming video content. I think over the Christmas holiday I might try to produce a few lessons in video and do a little experiment in flip teaching in the new year.
Over the weekend as a small project I built myself a tweeting motion detector. If someone moves inside the house an Arduino UNO is triggered to send an alarm message to my @mrgarduino twitter account. What would be even better would be to get a Raspberry Pi to send a photo as well from a webcam- will try to do this in the future. To make this project you need an Arduino, Ethernet shield and a motion sensor connected to PIN 4 of the Arduino. I also used an LED (set on PIN 6) to check when the motion sensor was triggered – it flashes every two seconds for 200ms but when an event triggers the sensor it stays on longer.You will also need the PString Library (Google is your friend) and check the network settings.
I run an extra-mural electronics club and we were lucky enough to get hold of some Arduinos – credit card sized computers that can be programmed from a PC and used in just about any project you can think of. The Students and myself basically get to tinker away with electronics which is awesome – watch this space for project updates. I also work with Sumbandila, a non-profit organisation in the field of secondary education which provides an educational outreach programme to impoverished rural children in Limpopo. Sumbandila ran a holiday school a few weeks ago and we got the students programing the Arduinos too! It was fantastic. We built a little traffic light LED shield (a circuit that mounts on top of the Arduino) and the students could program it themselves. It was very impressive to see these kids going from having a very limited knowledge of programming to getting all the LED traffic lights flashing in order – with minimal input from myself. Arduino is an open source system I would recommend to any ICT or Science department. Give it a go!
A few weeks ago, after an assembly I got all the staff and students in the school to write down four words that they felt described the ethos of our school. They did so anonymously and I compiled a list of all the words, ranking them for the amount of times that they re-occurred. Of course some of the students couldn’t resist. “Money grabbing” came up, as did oddly “have a nice day” but luckily those jokers where few and far between. The top word from the staff was “individuality” whilst the top word from the students was “respect”. Using a web-based program called tagxedo.com you can wrap the words around a shape and change their size to correlate to the number of times the students wrote the word down. Here are the results.