快猫短视频

Why do shoelaces with a circular cross section come undone more easily than those with a flatter cross section?

(Continued)

鈥� An earlier correspondent stated that, with flatter shoelaces, 鈥渢here is much more friction because there is a much greater contact area鈥�. But the force to overcome static friction is the product of the coefficient of friction for the two surfaces in contact and the force pressing them together. This is independent of contact area.

I know from my climbing days that different knots and hitches are more or less resistant to slippage: if one increases the number of turns on a hitch it holds better. So if it isn鈥檛 due to an increase in contact area, why do some knots hold better ? The answer must be that they tighten when under a load, increasing the force pressing them together.

Terence Hollingworth, Blagnac, France