Coins

I have an almighty collection of very clean 1 cent coins. No vending machine will take them, and I can rarely be bothered to look through my pockets at the checkout to find the exact change, and get a couple of coins more. If I empty the pockets carefully when I put the trousers in the wash, these coins end up on my floor. If not, they end up in the washing machine, then on my floor.

Yesterday I found a use for 1 cent coins: demonstrating the independence of horizontal and vertical motion. Some people are surprised by the following experiment, so I showed it to my student.


The three coins need to be in contact, and the two small coins must balanced on the edge of the table. Hold the top 2€ coin with one thumb, and flick the bottom 2€ coin towards it with the other hand. The top 1c should fly off much faster than the one on the left, but they should start to fall at the same time. See which coin hits the floor first. It helps here if the floor is hard enough for a coin to make a nice clink when it hits the floor.

If you do this in the pub (or anywhere where someone else does the cleaning up), you can dispose of 1c coins quickly and painlessly, and learn about the world at the same time.

Experimental Physics

The former right-back of Torpedo Entenhausen is trying to learn physics, and has hired me for private tuition. He is paying me in food, which suits us both fine.

His physics course sounds very boring. He sits through long lectures, and then sits in problem groups where the tutor solves the problem on the blackboard. After hours of tuition, he has done nothing himself, and learnt almost nothing. He has a full set of notes, but it would have been far cheaper and easier just to photocopy them all.

Over the past few years I have developed a very experimental view of physics. Physics should start with an experiment and end with an experiment. It is impossible to understand a physical property unless you can relate it to an experiment. His course doesn't seem to do experiments. Maybe it costs money, and takes too much effort. It is cheap and easy to write P=m*v, but expensive to find a cannon and a place to shoot it. The exam questions are full of mathematical detail, of vectors, equations and calculations, and of units. But they never ask "How do we know this?" or "How could you test this law?".

So yesterday, after a bout of mathematical problem solving, I tried to change matters. We did the following experiments, first in his garden, then in a children's playground:

1/ Vitamin pill rocket, as a demonstration of the conservation of momentum You put a fizzy pill in the lid of a tube of vitamin pills, and fill the tube 1/3 full of water. Reattach the lid, turn upside down and place on a flat surface and retreat. Lid pops off, Water goes down, tube goes up. Momentum conserved. Neighbours impressed.

2/ Roundabout, as a demonstration of the conservation of angular momentum. Get on. Start turning. Move to the middle, move to the outside. See when the roundabout turns faster.

3/ Roundabout, as a demonstration of the centrifugal force. Start turning, place ball on floor, watch ball.

4/ Roundabout, as a demonstration of the Coriolis force. Both get on. Start turning, throw ball to other person. Stop turning. Turn other way. Throw ball. Throw up.

I sadly forgot to take a pendulum on the roundabout to demonstrate the principle of the Foucault pendulum. Next week. I like roundabouts. Why are they only given to children? Why don't physics institutes have roundabouts in the Foyer?

I think I could get to like physics again, as long as I don't have to spend too much time with physicists, and as long as it isn't a job requirement.

Change of profile

I have changed the description of the blog. For the past few months it was subtitled:

"The diary of a soul who doesn't know what he's doing, or even trying to do, but is blogging it anyway".

A new job

I managed to do it. In the past 12 months I sent out 6 job applications. I kept trying to up the rate to at least once a week, but never managed it. I got invited to two interviews, so I'm rather surprised that I found a job. I've decided to keep the details of the job out of this blog in order to give it a decent chance of working.

The job doesn't require any knowledge of physics, which made applying for it a lot easier. I never got to the point of coming to terms with the depressed endings of the past two jobs well enough that I could talk about them with a bunch of strangers. It was a relief to not have to discuss the contents of my PhD at all. When applying for this job I was relieved not to have to explain why I'm an expert with glass tubes and ultrasound devices, while feeling my stomach turn with the weight of perceived failure.

So I've started something completely different. It should pay well enough for me to live comfortably, and hopefully won't interfere with my evenings and weekends too much. With a bit of luck I'll have some nice little projects to work on. At the moment that's all I want in life. My projects won't make me rich and famous and won't change the world, but I'm happy to leave that sort of stuff to others.