The passage highlights the intricate relationship between the physics of running and the mechanics of shoelace knots. Initially, as a runner's foot strikes the ground, the high acceleration—reaching up to 7 g—induces significant inertial forces on the shoelaces, which results in the knot experiencing pressure and deformation. Subsequently, as the shoe continues to move and the loose end of the lace elongates, the weight of this loose end contributes to the knot's failure over time. Ultimately, this process reveals that not only are the knots subject to the dynamic forces involved in running, but also that the bows of the shoelaces are equally vulnerable to being compromised by these physical stresses. Thus, the continual interplay of acceleration and inertia during running directly impacts the structural integrity of shoelace knots.
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.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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