Most of us know how to get a ribbon to curl , by swiftly force a scissor blade across the airfoil . You ’ve in all probability heard that the faster you do this , the tighter the curl . Physics begs to differ .
A tedious movement — mix with a sharp brand and just the right amount of tension on the ribbon — produces optimal curls , according to the latest experimentation by an international squad of physicists . Apaper about this body of work appearedin the Proceedings of the National Academy of Sciences last calendar month . leave author Anne Juel , of the University of Manchester in England , described the findings at ameeting of the American Physical Societylast calendar week .
Back in 2007 , co - authorBuddhapriya Chakrabartiof the University of Durhamperformed his own experimentsto trial the commonly held wisdom that the faster you scrape the blade , the plastered the ribbon will curl . He even built a special motorized curling apparatus for this purpose .
He seize formative ribbons — the kind of textile you might find in transparencies ( for anyone who still uses transparencies)—to the motor and let them hang over a alloy rod . Then he suspended various free weight on the end of the ribbon to perpetrate it taut and practice dissimilar amounts of pressure , and let the motor attract it across .
Chakrabati concluded that , wayward to conventional wisdom , you get a much stringent gyre “ if you hold the tension unceasing and if you make it go slower , ” hetold Scientific American .
The reason a ribbon roll in the first property is that the outer layer reach and expands more than the inner stratum being compress against the scissor blade . That ’s also why the decoration must be held taut : doing so pulls the molecules in the credit card asunder . Do this at a slightly slower speed , and it makes it harder for the plastic ribbon to rupture back to its anterior shape . It relax into a nice close curl alternatively .
When Juel learn about Chakrabati ’s work , she contacted him about collaborating on additional cogitation . Theyused a similar apparatus , with a ribbon wound onto a cylinder — the better to drag it across a sharp blade .
The new experiments let on that a sharper blade will stretch the medallion ’s outer stratum even more . Increasing the tension on the thread by adding laboured weights also resulted in tighter curl — up to a point . Beyond a certain threshold , that contortion will spread too deep into the ribbon , dampen the curve upshot . That makes sense : it ’s the remainder between the inner and outer layer , after all , that results in whorl in the first place .
Juel , Chakrabarti , and their colleagues also came up with a predictive mathematical model for optimal ribbon curling , balance such vista as the medallion ’s anatomical structure , blade acuteness , how much tension is applied to the ribbon , and how quickly the leaf blade is pulled across the palm . fundamentally , “ The tightest ringlet will be obtained when you negociate to go for a shipment that will bring proceeds to on the button half the thickness of the ribbon , ” Juelsaid at the meeting .
clean word of advice : not all ribbon are create equal . Satin ribbons , for instance , are waver , unlike pliant ribbons , which are a continuous sheet . So satin ribbons ca n’t be stretched or deformed in the same way . Running your scissor steel along a satin ribbon will just ruin it . And dissimilar types of ribbon will have different optimum tensions for the tightest curls .
[ American Physical Society , PNAS ]
mechanicsPhysicsScience
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