A strip of paper becomes a spiral, if you pull the strip between the thumb and the edge of a knife, pressing hard.
Zusammenfassung Englisch Origami, the age-old art of folding intricate three-dimensional structures from flat material, has found numerous applications in e.
The spiral becomes a curl where gravity is present. You use this effect to decorate the ends of synthetic materials, such as the narrow colourful strips or ribbons used in gift-wrapping.
I suppose that you have to explain this effect in the same way as a bimetallic bar. You create a bimetallic bar by glueing together two strips, each made of a different metal.
Once this bimetallic bar is heated, one metal strip expands more than the other causing the bar to bend. The reason that the strip of paper bends is not the difference in temperature between the top and bottom side.
The knife changes the structure of the surface of the paper. This side becomes 'shorter'. Origin: Sendung mit der Maus und TH Aachen Incidentally, a strip of paper will bend slightly if you hold it in the heat of a candle flame.
If, however, you turn hard single sheet origami end of another strip and glue the ends, the result is the so-called 'Moebius strip' on the right.
If you cut the ring on the left lengthways in the middle, then you have two rings.
Variations: If you cut the ring in the same way, expect a surprising result! Try it! The glueing area is green.
There are surprising results. Andreas Reichelt from Neckargemünd told me this playing with strips. By Martin Gardner.