The passage describes the significant impact of acceleration and inertia on the mechanics of shoelace knots during running. As an individual runs, their foot experiences accelerations that can reach up to 7 g, which underscores the high forces exerted on the shoelaces. Consequently, this force causes the knot to deform and put pressure on itself, ultimately leading to failure as the loose end of the lace begins to slip out. Additionally, the length of the loose end increases the weight that contributes to the knot’s instability, which further exacerbates the issue. Thus, the relationship between the physics of running and the performance of shoelace knots illustrates a complex interaction where increased physical forces can lead to eventual failure of the knot.
To break down the physics of the phenomena, the researchers attached a small device to the free end of the laces that measured acceleration, and then Gregg went for a walk or a jog. This acceleration creates inertia, which is the tendency for an object to keep moving once it is in motion.
“We were surprised that the accelerations were so high. They’re like 7 g [units of acceleration] ,” O’Reilly said. “By way of comparison, the highest g on a roller coaster are 6.3. Your foot is experiencing these really high g-forces as you’re running all the time. It’s a biomechanical miracle that all of that impact is absorbed through your body and spine.”
The knot itself is under pressure too. The videos showed as the shoelaces bounce up and down with each footfall, the main knot begins to deform. Once the knot opens sufficiently, then the free end of the lace, which is being tugged by inertia, begins to slip out.
The team built a robotic pendulum to examine the math on a deeper level. They found the knot’s failure intensifies overtime. As the length of the loose end increases, so too does its weight relative to the other strand. This trend adds to the inertial forces, until total shoelace failure. Moreover, the bows of your shoelace are not exempt for this flaw.
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Question
Use the passage to answer the question.
Analyze the interactions that develop over the course of the passage. In 3-5 sentences, explain the relationships between the physics of running and its impact on shoelace knots. Use transition words to sequence and connections.
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