[1] Pressure (p or P) is the force applied perpendicular to object's surface per unit area over which the force is distributed or the measurement of how an applied force is distributed over an area. 445 Gauge (gage) pressure is the pressure relative to the ambient pressure.
[1] Many units are used to express pressure. Some derive from a force unit divided by an area unit; the SI unit of pressure, the pascal (Pa), e.g., is 1 newton per square metre (N/m2).
Pressure is how an applied force distributes over an area. Mathematically it's defined as a force applied over an area: P or p = F/A.
P = pressure
F = normal force magnitude
A = surface contact area
Thus the greater the force over an area, the greater the pressure:
P = 29N/29m2 = 29 pa → 100N/29m2 = 3.45 Pa
F = 100 N
A = 29 m2
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This can shown by the application of snowshoes, which distributes the force applied on the snow to prevent the person from sinking in.
And lower force over the area or more force of the area, the lower pressure and force:
P = 29N/29m2 = 29 pa → 29N/100m2 = 0.29 Pa
[1] Pressure is a scalar quantity. It relates the vector area element (a vector normal to the surface) with the normal force acting on it. The pressure is the scalar proportionality constant that relates these two normal vectors:
Note: [1] The IUPAC recommendation for pressure is a lower-case p. But upper-case P is widely used. The usage of P vs p depends upon the study field.
[2] Pressure is also one of the main properties of air, alongside temperature, density, and humidity, which are directly proportional to each other. Air is a fluid composed of many gases.
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[2] Atmospheric pressure (AP) is the force exerted by the atmosphere's air on the Earth's surface, made by the air column's "weight" directly above the surface, since air has mass, hence Earth's ravity causes ti o have weight.
Each air molecule exerts some weight onto Earth's surface.
And thus the AP depsnds on the air molecule amount above the surface.
We can't feel AP since it acts equally (balanced) in all direction and is distributed around all objects.
[1] The pound-force per square inch (PSI, symbol lbf/in2) is the traditional pressure unit in imperial and US customary systems.
Pressure may also be written in terms of standard AP; the unit atmosphere (atm) is equal to this pressure, and the torr is defined as 1⁄760 of this. Manometric units like the centimetre of water, millimetre of mercury, and inch of mercury are used to express pressures in terms of the height of column of a particular fluid in a manometer.
[2] Thought we often use pascal to measure pressure (1 Pa = 1 N/m2), metherologists usehectopascal: hPa = 100 Pa.
The most often used pressure units are:
Pounds per square inch (PSI)
Millibars (mb)
Inches of mercury (InHg)
Millimeters of mercurcy (mmHg)
[2] The most common conversion factors are:
[2] A barometer is a device used to measure pressure, which is classified into 2 main types: The aneroid and mercury barometers.
The mercury barometer is further classified into fixed--cistern (Kew) and adjustable-cistern (Fortin)
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[2] A mercurcy barometer comprises of a vacuum glass tube closed at the top and open at the bottom. The tube is partially submerged in a cistern/mercury-filled bucket. This setup causes AP to push mercury in the cistern to force the cistern up to the tube but simultaneously, the mercury's weight will counteract this. Thus, the column's height directly on the AP.
[2] Thus If AP lowers, so will the mercury column's height. If the AP increases, so will the column's height
[2] An aneroid barometer consists of a sealed capsule with a constant pressure in it, designed for AP to enter it to compress its capsule. This allows the capsul to contract/expand depending on local AP changes. Since the capsule connects by means of gears on the needle, the AP's corresponding value is indicated.
Barometric altimeters use the same principles but IO indicating the pressure they're calibrated to indicate corresponding atttitudes.
https://youtu.be/PGH0pN346dw: research stopped at 7:20.