Staying Dry Under Water!

Ever seen Pirates of the Carribean? Captain Jack Sparrow and William Turner manage to sink a boat under the water, maintaining the air bubble inside, and breathing! piratesunderwater

But is this really possible??

Technically, it is possible! Here is a very easy, very quick experiment to do in your own kitchen or bathroom that shows why they can breathe the air trapped in the boat:
1) Fill a bucket or your bath tub with water about one foot deep. (Or as deep as your tallest cup)

2) Take a cup, preferably a clear glass, and tape a little piece of paper inside the cup, at the very bottom. (see the picture below)

3) Turn your cup upside-down, make sure no paper is sticking out of the opening (keep it all inside the cup, as in the picture below)

4) Make sure you keep the cup completely upside-down! Do not tilt it at all, especially in the water. (Just like the picture below)


5) Keeping the cup perfectly upside-down, slowly lower it into the bucket or your bath tub. Put the cup under the water’s surface, you should feel the cup trying to push back up a little bit…slowly bring the cup STRAIGHT up out of the water, keeping it upside-down still! (Remember, no tilting the cup…)

6) Dry the cup off, then flip it over and look inside…the paper taped in the bottom should still be dry!!

7) For fun, try putting them cup upside-down into the water, then tilting the cup to the side slowly (just a little bit), water will rush in this time since you tilted it, and the paper will get wet.

Why does this happen? When you tip the cup upside down and insert it into the water, the pressure is evenly distributed inside the cup, and water cannot rush in, keeping the paper dry. If you tilt the cup, water rushes in and gets the paper wet. In Pirates of the Carribean, the boat is much too heavy to bring down to the bottom…think about how the cup exerts a buoyant force on your hand even when you push it down a few inches. The weight required to get a boat to sink while upside-down would be far greater than just the weight of Will Turner and Jack Sparrow, but in theory it could be done if you used weights, or a lot of people. Since the air is in the boat there would be a limited supply of oxygen, so you could breathe, but not for long.

-Steve Yu

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