Physics of ribbon curling unravelled

Scientists have explained precisely how and why a ribbon curls when we run a scissor blade down one side of it. They teased out the effects of the blade’s sharpness, the tension applied to the ribbon and the speed it moves.As the ribbon bends around the blade, its outermost side stretches and permanently deforms, producing curls.Sharper blades and slower movement make tighter curls – but the pulling force has an ideal strength, above which the curls become less pronounced.

The UK-based team will present the study on Wednesday at the March Meeting of the American Physical Society in Baltimore; it also appeared last month in the journal PNAS. In their experiments, a thin ribbon – made in this case from a transparent PVC film – was draped over a blade and a weight was hung from the end. The ribbon was then wound onto a cylinder in order to drag it across the blade. The team measured the width of curls produced by different weights and winding speeds – and also created a mathematical model to show that these could be explained by predictable changes in the structure of the ribbon. Source: Physics of ribbon curling unravelled

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