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J. Perelman
"Entertaining physics". Book 1.
Chapter 5. Properties of liquids and gases


That fluid pressure is exerted downward on the bottom of the vessel, and sideways on the wall, you know and even those who have never studied physics. But what they are pressed and up , many do not even know. Ordinary lamp glass will help to ensure that such pressure exists. Cut out the cardboard circle such size that it covers the hole of the glass tube. Attach it to the edges of the glass and dip into the water, as shown in the figure.

A simple way to make sure that the fluid pressure from the bottom up.

That circle had not fallen when submerged, it can hold strings stretched across its centre, or simply press with your finger. Put the glass up to a certain depth, you will notice that the circle is well kept and himself, not presses either finger pressure or tension of the thread: it holds water, pressing on it from the bottom up.

You can even measure the magnitude of this pressure up. Pour carefully into the glass of water; as soon as the level inside the glass closer to the level in the vessel, the circle disappears. Hence, the water pressure on the bottom circle is balanced by the pressure on him from the top of the water column, the height of which is equal to the depth of the circle under the water. That is the law of fluid pressure on any submerged body. Here, incidentally, is the “loss” weight in liquids, which tells the famous Archimedes law.

Having multiple lamp glasses of different shapes but with the same holes, you will be able to check and another law relating to liquids, namely, the fluid pressure at the bottom of the vessel depends only on the bottom area and height, the shape of the vessel it is completely independent. The test will be, what will you do now described the experience with different lenses, securing them at the same depth (which must be pre-glued to the glass of the paper strip at the same altitude). You will notice that the circle every time will fall away at the same water level in the glass.

Fluid pressure at the bottom of the vessel depends only on the bottom area and the height of the liquid level.
The figure shows how to verify this rule.

Hence, the pressure of the water columns of different forms of the same, unless the same base and height. Note that here it is important height , not length, because of the long sloping pillar presses on the bottom is exactly the same as a short vertical post similar height with an equal area basis).

Entertaining physics J. Perelman


System Orphus


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