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| This Never Happened |
In the 1980s, every sitcom had a scene where a strong man tries to open a glass jar to no avail only to be followed by a slight woman who would then open it easily, to great surprise and applause. Every sitcom did it. They had to. I believe it was actually legally required, signed into law by Reagan though I can't officially back that up with paperwork.
Not willing to ascribe this trend as mere fancy (if 80s sitcoms be not truth, then what is life?), I've thought very hard about how this could be explained - very hard, I should have been working - how it could be true, and come up with a not entirely implausible working theory.
First let's start with the evidence we have from one of the sitcoms - a data point, if you will. In the scene from <DELETED>, the source of the screenshot above, the slight woman accomplishes her task through a specific technique. She puts her ear to the jar, shakes it, listens to the sound, hits it from the bottom in just the right way (presumably using the audio data just obtained) and then opens it easily in the usual twisting manner. And if any man should wish to prove how this sequence of events may add up to a cogent explanation, let him write a blog, he is a wiser man than myself.
I can't make that work but here's how I think it could work, generally.
The muscular man, expending all his might, hunkers down, gripping the jar lid like Eleazar's sword. But a great proportion of his strength going toward firm grip, he works against himself to his own detriment. The tight grip has the effect of squeezing the lid, increasing the friction between the lid and the jar rim. The rotational force, though significant, is not greater than the resistance his own grip is creating - the two are cancelling each other out and he can no wise get relief.
And now you can guess what happens with the slight woman. Not having an iron grip, there is less friction in the lid and then a lesser strength will open the jar, paradoxical though it may seem.
This is all only theory, of course. Being lazy and unlearned, I have done 0 experiments, gathered no data and haven't done so much as glanced at an equation. And, of course, Mythbusters is not answering my letters. But it does make sense and I posit it as likely an answer to a well-worn riddle as you'll find anywhere.
And so the lesson is this: the race is not to the swift, nor to the battle to the strong... When opening hard-to-open jars, apply the maximum torque while applying the least possible grip necessary for the task.
