My answer to What is water pressure?
Answer by Arûn Râinâ:
Pressure (symbol: p or P) is theapplied perpendicular to the surface of an object per unit over which that force is distributed. (also spelled gage pressure)is the pressure relative to the ambient pressure.
Variousare used to express pressure. Some of these derive from a unit of force divided by a unit of area; the unit of pressure, the (Pa), for example, is one per ; similarly, the per ( ) is the traditional unit of pressure in the and systems. Manometric units such as the , , and are used to express pressures in terms of the height of in a manometer.
Pressure is the amount of force acting per unit area. The symbol for pressure is p or P.Therecommendation for pressure is a lower-case p.
However, upper-case P is widely used. The usage of P vs p depends on the field in which one is working, on the nearby presence of other symbols for quantities such asand , and on writing style.
P is the pressure,
F is the,
A is the area of the surface on contact.
Pressure is aquantity. It relates the vector surface element (a vector normal to the surface) with the normal force acting on it. The pressure is the scalar that relates the two normal vectors:
When a person swims under the water, water pressure is felt acting on the person's eardrums. The deeper that person swims, the greater the pressure. The pressure felt is due to the weight of the water above the person. As someone swims deeper, there is more water above the person and therefore greater pressure. The pressure a liquid exerts depends on its depth.
Liquid pressure also depends on the density of the liquid. If someone was submerged in a liquid more dense than water, the pressure would be correspondingly greater. The pressure due to a liquid in liquid columns of constant density or at a depth within a substance is represented by the following formula:
p is liquid pressure
g is gravity at the surface of overlaying material
ρ isof liquid
h is height of liquid column or depth within a substance
Another way of saying this same formula is the following: