They found that when running, your foot strikes the ground at seven times the force of gravity. They tied shoelaces to the pendulum arm and weighted the laces to mimic the forces of the swinging leg. This explains why when walking to the park your shoelace knots seem completely in tact, but of course as soon as you start running, when it really counts, they inconveniently come undone.
This is published unedited from the IANS feed.
The stomping and whipping forces of your leg moving and foot hitting the ground are the reasons you have to keep bending over to tie that pesky shoe in the most untimely circumstances-like on the steps going up from the subway. Details of the study were described in the journal Proceedings of the Royal Society A.
Oliver O'Reilly, from the University of California, Berkeley, said that the research was inspired by personal experience. "If we understand how simple knots work and fail, we can understand more complex knots", he says.
"We didn't specifically study double knots, but we know from anecdotal evidence that they sometimes still fail, though less frequently than single knots", Gregg said. All that impact makes the knot in your laces stretch and then relax while the action of swinging your leg pulls on the end of your laces.
The researchers concluded that while it doesn't always happen before you take your shoes off, the unwanted untying would always happen in the end if you ran for long enough.
Engineering researchers say they have solved the riddle of why shoelaces come undone.
No matter how tight you tug, it feels like some shoelaces are doomed to come untied. The new paper examines how weak and strong knots react to the application of force during sustained periods of running, shedding light onto a common problem that has troubled humans for millennia.
Researchers at the University of California, Berkeley, chose to find the answer, which was published Tuesday in the journal Proceedings of the Royal Society A. Graduate student Christine Gregg, a co-author of the study and also a runner, got on treadmill while her colleagues filmed her shoes.
The researchers also tested their theory that increasing inertial forces on the free ends would trigger runaway failure of the knot.
The study authors concluded that it's the combination of the loosening forces of our foot stomps on the knot and the inertial forces on the shoelace ends and loops that lead to lace unravelling.
We've all experienced it.you tie your shoelaces and go for a walk, and somehow your shoelaces become untied. Scientists still need further studies to figure out why one knot is stronger than the other. More research needs to be carried out to understand all the variables involved, they said.
Added Ms Gregg: "The interesting thing about this mechanism is your laces can be fine for a really long time, and it is not until you get one little bit of motion to cause loosening that starts this avalanche effect leading to knot failure".