Another bad physics joke

Brrrrr.  It was so cold this morning I had to wipe the Bose-Einstein condensation off the windows.

Perhaps more amusing was the sight I saw on the edge of the road this morning on my way into work. The ‘white-line painting crew’ had clearly been out remarking the road. The white line on the left hand edge of the road was now brilliantly clear, and went straight over the top of a squished possum. The question is, was it the line-marking machine that squished the possum, or could the crew just not be bothered to move the carcass?

On a more physics note, I’ve been puzzling for a couple of weeks why the underneath of our laundry tub gets damp every time the washing machine is in use. I’d felt around for leaks on the hoses, taps, etc, or leaks in the waste-water plumbing. I’d even waited and watched the machine go through most of a cycle (and just  my luck in that cycle no water appeared at all). Yesterday I solved the problem, however, by systematic investigation of the likely sites for a leak. As it turned out, the cold-water hose wasn’t securely attached to the cold-water pipe.

How come that happened? It seems as if it’s unscrewed itself. Maybe that’s not so surprising given the way the hoses twitch when the machine opens and closes its inlets. When the water is flowing into the machine, it’s got momentum. When the machine closes its inlet ports, as it does several times a cycle, it does it really fast. The water in the hose now stops moving, decelerating very quickly. This rapid change in momentum corresponds to a force, which is felt both at the machine end of the hose and at the attachment to the water pipe, and is responsible for the characteristic banging noise that transmits itself along the water-pipe network of the house. The hoses visibly twitch when this happens. My guess is that the cumulative effect of this has unscrewed the hose a little – about a quarter of a turn; enough to cause a bit of water to escape.

 Oh, and finally, before you ask, our baby hasn’t arrived yet. We’re drifting into the frustrated-wait stage now…



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