Physics · the experiment
Lock the rope without friction
Strands coiled like springs, no sleeve, no friction. Four questions, from beginner to expert, on what holds a cut bundle together, or makes it come apart.
1 · Find what holds the bundle
Beginner
What holds a cut bundle of naturally coiled strands together?
2 · Measure how sharp the line is
In the frictionless simulations, two strands with a pitch of 4 diameters lock with a preferred radius of 0.38 diameters, and unravel with 0.375 diameters.
Intermediate
By what percentage did the preferred radius drop between the two cases?
3 · Try enormous friction
Straight strands, twisted together then cut, unwind. The authors vary the friction coefficient between strands from 0 to 100.
Expert
Does enormous friction, with a coefficient of 100, stop them from unwinding?
4 · Make the bundle longer
When a bundle fails, an unravelling front forms at the free ends and travels along the bundle keeping the same shape and stored energy, like a solitary wave. The simulations range from 40 to 320 diameters in length.
Expert
With the same shapes, does a bundle twice as long hold better?
Rope locked
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