Friction. Force. Pressure. And why corkscrews have worms.
There is a tremendous amount of friction between a cork and the wine bottle it is in. After all, the cork typically has a wider diameter than the bottle opening, and was squeezed in. As a result, substantial force is needed to pull out the cork.
We would have some difficulty if we did it with our bare hands, partly because the cork is often flush with the mouth of the bottle, and partly because even if it was sticking out, the cork would be too smooth and there would likely not be enough friction to grip it forcefully.
This is where a corkscrew comes in handy. The secret lies in the curly-wurly metal piece found on a typical corkscrew. Called the helix or the worm, its does three things for us:
1) Its sharp pointy end means that the force will be applied to a very small area; the resultant pressure (Pressure = Force/Area, i.e. force per unit area) is high, making it easy for it to first penetrate the cork and then to twist deeper into the cork.
2) Twisting the corkscrew means the worm will become embedded in the cork; there will be much greater friction when we subsequently attempt to pull the cork out.
3) The curly-wurly shape results in more surface area in contact with the cork; this adds to the friction when we pull the corkscrew out, making it easier for the cork to be pulled out.
This is one instance where being called a worm is a compliment!
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