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  • 22 Feb 22

    Pool ball analysis

    One of my students is doing his IA on the relationship between the perpendicular distance between the direction of a pool ball and the centre of a ball that it hits and the angle between the original direction and the direction of the ball...

  • 17 Feb 22

    Why two lamps don't interfere

    Why don't two lamps  interfere with each other? The reason is that they are not coherent. Each lamp is made of a large number of atomic wave sources that have random phase, the wavefront produced from each lamp changes with time so any interference...

  • 5 Feb 22

    Newton´s pigs

    One of my student's sent me a question about the classic pig in an elevator problem. "Hi Chris, how can it be that the normal force is calculated these two different ways when the elevator is accelerating downwards and upwards?" v

  • 26 Jan 22


    Today I asked my class, of which Adriana from Romania was a member, to explain why the temperature of an insulated cylinder of gas will increase when the volume is reduced. The rather fragmented explanations led me to spend some time talking...

  • 3 Jan 22

    A river runs through it

    It was a white Christmas but a wet new year so the stream that runs under our house is in full flow. I posted this photo on facebook and within seconds one of my former students, Erik Torstensson, commented about installing turbine. So I thought...

  • 1 Jan 22

    Christmas tree lights puzzle

    I have just been taking down the lights from our Christmas tree and noticed something interesting. One set had a transformer the other didn't. The one that didn't had 70 LEDs arranged in series. The pd across each was only 220/70 which is about...

  • 28 Nov 21

    Swimming pool investigations

    There is a swimming pool next to my school, I thought it might be fun to think up some investigations that could be carried out there, here's a quick list: That'll do for now.