Your shoe's untied!

We have all had the minor ivconviencene of our shoes coming untied, or that one jerk of a friend who tells you they're untied but are really not.
However, have you ever wondered what forces are behind the problem? A new study conducted by researchers at the University of California, Berkeley and published in the Proceedings of the Royal Society A explains exactly why shoelaces come loose. The force: “a double whammy” of stomping and whipping forces that act like an invisible hand loosening the knot and tugging on the free ends of the laces.

Researches filmed a runner in slow motion while running in many types of different shoes. It was determined that the average foot strikes the ground at about seven times the force of gravity. The knot of the laces responds to this force by stretching and expanding. Finally, the swinging of the leg applies an inertial force on the ends of the laces, eventually causing the knot to fail.

It is surprising how many forces are acting on us in a daily basis without us even knowing.