We study the pressure of the liquid. Draw conclusions

To deal with the issue of "Fluid Pressure", let's start with the classic examples and gradually move on to more complex and confusing options. For a vessel of cylindrical shape, whose walls are strictly vertical, and the bottom is horizontal, the hydrostatic pressure of the liquid poured into the height h will remain unchanged for each point of the bottom. The formula for calculating this value will look like p = rgh, where r is the density of the fluid; G - acceleration of gravity; H is the height of the liquid column. The value of p for all points of the bottom is the same.

By entering the area of the bottom of the vessel S into the formula, we can calculate the pressure F. Assuming that the fluid pressure at the bottom of the vessel is the same at each point, the logical conclusion is F = rghS.

It is easy to see that in this case the pressure force on the bottom is equal to the weight of the liquid poured into a cylindrical vessel of regular shape. It seems paradoxical, but it has a scientific and logical explanation saying that the formula F = rghS works for vessels of very different shapes. In other words, for equal S-the bottom area and h-the height of the liquid level, the pressure of the liquid on the bottom is the same for all vessels, regardless of how much each individual vessel holds. At the same time, the weight of a really poured liquid into vessels of arbitrary shape may be less, and more than the pressure force on the bottom, but it will always satisfy the rule described above.

Following the basic principle of physics to check theoretical conclusions in practice, Pascal suggested using an instrument named after his name. The highlight of this device is a special stand that allows you to fix vessels of various shapes that lack a bottom. The bottom of the vessels is tightly pressed from below the plate, which is on one arm of the balance beam.

We install the weight on the cup of the other rocker and start filling the vessel with water. When the fluid pressure creates a force that exceeds the weight of the weights, the liquid will open the plate and the excess will flow out. By measuring the height of the water column, you can calculate the numerical value of the force of its pressure on the bottom and compare it with the weight of the weight.

Taking into account the possibility of achieving a greater pressure force with a small amount of water, only by increasing the height of the water column, one more explanation can be given to an interesting experience, also described by Pascal.

To the top cover of a new carefully troweled barrel, to the edges filled with water, was attached a long tube, over which water was poured. The tube had a small cross-section, a pair of water cups was enough to lift the water column to a considerable height. At some point a new solid barrel could not stand it and burst at the seams. Regardless of the amount of liquid poured, it was the height of the water column that led to an increase in pressure on the bottom of the barrel. As a result, a critical force was created, which led to a rupture of the tank.

The difference in the real weight of the fluid and the pressure force on the bottom of the vessel is compensated for by the force that causes the pressure of the liquid on the walls of the vessel. It is the slope of the walls of the vessel that leads to this pressure being either directed upward or downward, respectively, bringing the system into equilibrium.

The vessel, which has a narrowing to the top, experiences a liquid pressure directed upwards. Interesting experience can be done by preparing a simple installation. It is necessary to put a cylinder on the fixed piston, which passes into a tube installed vertically. Filling water through the tube, we observe how filling the space above the piston leads to a rise of the cylinder up.

In summary, the term "pressure" can be defined as the ratio of the force that acts perpendicularly to the surface, to its area. The unit pressure is a value equal to one Pascal (1 Pa) and corresponding to the action of force in one Newton (1 H) per one square meter (1 square meter).

According to the Pascal Law, the pressure experienced by the liquid (gas) is transmitted unchanged to each point of the volume of the liquid (gas). The intrinsic pressure of the liquid (gas) is the same at a specific altitude. With depth it increases.