Pressure is the ratio of a force that acts perpendicular to a surface, to the area of that surface. The pressure in pascals is measured (1 Pa is the pressure that a force of 1 Newton produces when applied to a surface of one square meter).
Pressure force is the force exerted by pressure on a certain surface. It is measured in Newtons (1 N). The smaller the surface area on which this pressure is exerted, the smaller the applied force can be, with which you can achieve the expected effect.
The force of pressure acts on the surface perpendicular to it. It cannot be identified with pressure. To determine the pressure, it is necessary to divide its force by the surface area on which it appears. If the same force is applied to act on surfaces of different areas, then the pressure will be greater where the bearing area is smaller. If the pressure and surface area are known, then you can find out the force of pressure by multiplying the pressure by the area.
The force of normal pressure is always necessarily directed perpendicular to the surface on which it affects. According to Newton’s third law, it equals the reaction force of the support modulo it.
Any force can play the role of pressure force. This may be the weight that deforms the support, or the force pressing a body to a certain surface, and so on.
When in contact with solids, liquids act on them with a certain force, which they call it - pressure force. In everyday life, you can feel the effect of such a force by covering with your finger the opening of the tap from which water flows. If mercury is poured into a rubber balloon, it can be seen that its walls begin to bulge outward. Fluid pressure can also affect other fluids.
When solids come into contact, the elastic force arises when their shape or volume changes. In liquids, such forces do not arise when the shape changes. The lack of elasticity with respect to changes in shape determines the mobility of liquids. When compressing liquids (changing their volumes), elastic forces will appear. They are called pressure force. That is, if the liquid acts on other bodies in contact with it with pressure, it means that it is in a compressed state. The more compressed the fluid, the more powerful the pressure resulting from this force will be.
As a result of compression, the density of substances increases, so liquids have elasticity, which manifests itself in relation to their density. If the vessel is closed with a piston and a load is placed on top, then when the piston is lowered, the liquid will begin to compress. A pressure force will arise in it, which will balance the weight of the piston with the load on it. If you continue to increase the load on the piston, the fluid will continue to compress, and the increasing pressure force will be aimed at balancing the load.
All liquids (to a greater or lesser extent) are capable of being compressed, therefore it is possible to measure the degree of their compression, which corresponds to a certain pressure force.
To reduce the pressure on the surface, if it is impossible to reduce the force, it is necessary to increase the area of the support. And vice versa, to increase the pressure, it is necessary to reduce the area over which its force acts.
The gas molecules are not connected (or too weakly connected) with each other by the force of interaction. Therefore, they move randomly, almost freely, filling the entire volume of the vessel provided to them. In this regard, the properties of gas differ from the properties of liquids. For gases, density is much more dependent on pressure than for liquids. The common thing between them is that the pressure of both liquid and gas does not depend on the shape of the vessel into which they can be placed.