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[Phys-L] Articulating Chocks

I walked out of the terminal at Quartz Mountain Airport on Saturday. A northerly breeze was blowing perhaps 7 mph down the runway. I went to walk past the waist high stand parallel to the runway where pairs of wooden wheel-chocks are stored, and of the ten pairs, there was one pair swinging East-West in the Northerly breeze.

I knew that nobody had just hung them up so I stopped and watched.The chocks are 12 inches long, with a cross-section of a right triangle of two equal sides and an hypotenuse measuring about  five inches. A pair is joined by 2 ft of 1/2 inch rope tied at a hole perforated at one acute apex end of each of them.

And I saw what was happening. Though chocks on either side were steady, this pair touched near their ends, and as the nearer chock swung away at an angle of perhaps 130 degrees to the breeze, at the limit, it pivoted so that its trailing edge, now leading edge made an angle of perhaps 80 degrees to the wind, and that was enough.    Now I had learned the trick, I set another pair with a long face at 130 degrees to the wind and had it pivoting on its partner too.

An object lesson on the flutter encouraged by too much mass after the hinge point.