Surprised? Let’s take a look at the forces at work…
Researchers at UC Berkeley, Oliver M. O’Reilly, a professor of mechanical engineering, and students Christine E. Gregg and Christopher A. Dailey Diamond, who are pursuing a Ph.D. in mechanical engineering have unraveled one of life’s enduring mysteries: why do shoelaces come undone
The answer…a complex interaction of forces, loosening the knot and then tugging on the free ends of your laces until the whole thing unravels.
The scientists captured a slow-motion video of a runner on a treadmill as seen on the right. They found that the foot strikes the ground at seven times the force of gravity and as the fabric of the shoe squashes down on impact, extra lace is freed at the top of the shoe, causing the knot to loosen slightly with each stride. Meanwhile, the swinging leg causes the lace’s free ends to whip back and forth tugging them outwards. As the knot loosens, the friction holding the knot tight decreases, and as the free ends lengthen, the whipping force goes up, leading to an avalanche effect, leading to knot failure.
Why is this even a study?
Christopher Daily-Diamond answers, “When you talk about knotted structures, if you can start to understand the shoelace, then you can apply it to other things, like DNA or microstructures, that fail under dynamic forces.”
Delvin, K. (2017, April 12). Scientists unravel mystery of the loose shoelace. The Guardian Retrieved from http://www.theguradian.com
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