Physics · Level 1 · Foundation
The roles of impact and inertia in the failure of a shoelace knot
Daily-Diamond CA, Gregg CE, O’Reilly OM (2017). Proceedings of the Royal Society A. doi:10.1098/rspa.2016.0770 · CC BY 4.0
Step 1 of 2Read the paper
Why do shoelaces suddenly come undone while you walk? The authors filmed a runner’s laces in slow motion, measured how hard the knot is jolted when a foot hits the ground, then built a swinging pendulum rig to test how impact direction, extra weight on the lace ends and the type of knot change how fast a knot slips loose.
How to read it
- Section 1 and Figure 1: the simple walking, swinging and stomping observations that started the whole study.
- Section 3 lists the hypothesised failure steps (i)–(v); read them slowly before the experiments.
- Section 4b explains the pendulum rig, the knot template and how "average slip rate" is measured.
- Section 5 and Figures 9–13 give the results; the Conclusion lists what the authors did not test.
Step 2 of 2Take the test
5 questions · about 30 minutes including reading · pick an answer to see straight away if it’s right. Nothing is saved.
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Paper: Daily-Diamond CA, Gregg CE, O’Reilly OM, Proceedings of the Royal Society A (2017), licensed CC BY 4.0. Summary and questions are Research Nest’s own; read the original for the full study.