Unit of Pressure - Unit, Types, FAQs
Pressure is the force exerted per unit area of any surface. The formula for pressure is P = F/A, where F is the force which acts perpendicularly upon any surface whose area A is described. Pressure is a vital concept in both science and daily life. It allows us to understand how air, water, and other forces act on different objects. From inflating a tire and operating hydraulic lifts to the operation of airplane wings and even vehicle brakes, pressure finds an application everywhere. Even in our body, one of the examples related to pressure is blood pressure. Learning about pressure, its units, and how it varies either with force or area helps students relate physics to everyday life quite easily.
This Story also Contains
- What is Pressure?
- Unit of Pressure
- Types of Pressure
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What is Pressure?
Pressure is the force applied per unit area on a surface. In simple words, it tells us how much force is acting on a particular area. The formula for pressure is:
$
\text { Pressure }=\frac{\text { Force }}{\text { Area }}
$
If the same force acts on a smaller area, the pressure is higher; and if it acts on a larger area, the pressure is lower. For example, a sharp knife cuts better than a blunt one because the sharp edge has a smaller area, creating more pressure. The SI unit of pressure is the Pascal (Pa), which equals 1 Newton per square meter $\left(\mathrm{N} / \mathrm{m}^2\right)$. Pressure plays an important role in daily life, from inflating tires to blood flow in our body.
Unit of Pressure
The unknown quantities are compared to a unit, which is a standard quantity. A specified magnitude of a physical quantity that has been adopted by law or convention is defined. For example, pascal (Pa) is the unit for pressure.
| System of Units | Unit of Pressure | Symbol | Relation / Remarks |
| SI System | Pascal | Pa | 1 Pa = 1 N/m² |
| CGS System | Barye | Ba | 1 Ba = 0.1 Pa |
| FPS System | Pound per square inch | psi | 1 psi ≈ 6895 Pa |
| MKS System | Newton per square meter | N/m² | Same as Pascal |
| Atmospheric Unit | Standard atmosphere | atm | 1 atm = 1.013 × 10⁵ Pa |
| Torr Unit | Millimeter of mercury | mmHg or Torr | 1 Torr ≈ 133.3 Pa |
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Types of Pressure
Fluid pressure:
The compressive tension at a point within a fluid is commonly referred to as fluid pressure.
Fluid pressure can occur in one of two situations: open channel flow, such as in the atmosphere, or closed channel flow, such as in the ocean.
In most cases, pressure in open conditions can be approximated by pressure in "static" or non-moving conditions, since the motions cause relatively minor variations in pressure. Such circumstances are consistent with fluid statics principles. The hydrostatic pressure is the pressure in a non-moving (static) fluid at any given place. Closed bodies of fluid are either "static" or "dynamic," depending on whether the fluid may move, as in a pipe or by squeezing an air gap in a closed container. The pressure in closed situations is consistent with fluid dynamics principles.
Vapour pressure:
Vapour pressure is a measurement of a vapour in thermal equilibrium with its condensed phases in a closed environment.. All liquids and solids have a potential to evaporate into gas, and all vapours have a potential to condense back into their liquid or solid state. The temperature at which the vapour pressure equals the ambient air pressure is known as the normal boiling point of a liquid which is the boiling point of a liquid under atmospheric pressure. Partial vapour pressure is the surface tension that a single component in a mixture contributes to the ambient pressure in the system.
Liquid pressure:
Water pressure acts on a person's eardrums while he or she dives under the water. The stronger the pressure, the deeper the swimmer swims. The weight of the water above the individual is causing the pressure. As a swimmer swims deeper, there is more water above them, resulting in increased pressure. The pressure exerted by a liquid is proportional to its depth. The density of the liquid also affects liquid pressure. The pressure would be higher if someone was submerged in a liquid that was denser than water. As a result, we may state that depth, density, and liquid pressure are all proportional.
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Frequently Asked Questions (FAQs)
Pressure is defined as the force applied perpendicular to an object's surface per unit area across which that force is diffused.
P=F/A
Where, the pressure is P, the normal force is F, and the area of the surface on contact is A.
The pascal (Pa) is a SI unit or MKS unit for pressure, equivalent to one newton per square metre (N/m2, or kgms2).
The CGS unit of pressure is equal to 1 dyn.cm-2 or 0.1 Pa.
The pressure within Earth's atmosphere, often known as atmospheric pressure or barometric pressure. The gravitational attraction of the planet on the atmospheric gases above the surface causes atmospheric pressure.
The applications of atmospheric pressure is that,
When a man sucks fluid from a straw, for example, the pressure within is moderately low, and the atmospheric pressure outside drives up the fluid into the straw.
When a vacuum cleaner is powered on, the pressure inside plunges off due to air inside.
The pascal (Pa) is the SI unit of pressure, which is defined as a force of one Newton per square metre.
The calculation is as follows for converting between atm, Pa, and torr, 101325 Pa =760 torr=1 atm.
It's sometimes referred to as a reference or standard pressure.