Posted on 08 September 2011 at 12:47h

I always think about physics when I travel on the boat between Rysjedalsvika (bet non nordics can't pronounce that one) and Bergen. This is most likely because  am always on the way to or back from a workshop. A couple of months ago I noticed the thing in the photo. It's suspended bridge for getting onto boats, a sort of cantilever. Kant is Norwegian for edge, this seems to fit nicely with what a cantilever is; a lever fixed at one end to an edge. I wondered if this cantilever is actually kantilever in Norwegian but it isn't. The cantilever in the photo (it was raining hence the blobs of water on the window of the boat) is supported by a rope at one end. As one walks along the bridge the tension in the rope will increase. The component of tension that supports the end is Tsinθ so if the rope has to support a weight W the Tension will be W/sinθ. So the tension depends on the angle between the rope and the plank. I wonder if the person who built this calculated the Tension or if they just attached the rope to the most convenient tree.  Builders have a very good feeling for this sort of thing, they may not understand how to take components but they know what the angle should be. Reminds me of one of the TOK essay titles on offer this year;

"4. When should we discard explanations that are intuitively appealing?" Not this time it seems.

Yesterday afternoon I walked into the staffroom, sat down with my cup of coffee and joined in a lively discussion on TOK. After about 10 minutes and several failed attempts by me to change the subject from TOK to something else, I realised that I had walked in on a meeting of the TOK teachers. Oops. Quick exit.