Why do your shoelaces come untied?


UC Berkeley mechanical engineers have shown why your shoelaces keep coming untied. It’s a question that everyone asks themselves, often after stopping to retie their shoes, yet no one had investigated. The answer, the study suggests, is that a double whammy of stomping and whipping forces act like an invisible hand, loosening the knot and then tugging on the free ends of your laces until the whole thing unravels.
Using a slow-motion camera and a series of experiments, the study shows that shoelace knot failure happens in a matter of seconds, triggered by a complex interaction of forces. The study is more than an example of science answering a seemingly obvious question. A better understanding of knot mechanics is needed for sharper insight into how knotted structures fail under a variety of forces.