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Types of Pressure

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Pressure is the force applied per unit area of an object. It is also called the per unit force on an Area. There are various types of pressure that we encounter in our daily life including atmospheric pressure, Gauge pressure, etc. Pressure is calculated by taking the ratio of the force applied to the surface area of the object.

In this article, pressure, its formula, its types, and others are in detail.

Pressure Definition

Pressure is defined as the force applied at the right angles to the surface of an object per unit area over which that force is distributed. There are specified sensors to measure the different types of pressure.

Pressure is defined as the Force per unit area. This directly means area affects the amount of pressure applied, if the area on which the force is applied is less, the pressure is less if the area is large on which force is applied. 

The SI unit for pressure is N/m2. Also, Different types of Pressure have different units in standard form.

Pressure Formula

The formula used to calculate the applied pressure is,

  • P = F/A
  • P = mg/A

where,
P is the Pressure
F is the Magnitude of the Force Applied
A is the Surface Area in Contact

Unit of Pressure

The SI unit of pressure is Pascal (Pa) and is denoted by the letter ‘p’. We know that pressure is a scalar quantity and Its formula is

P = F/A

Thus, we measure pressure in general units as, kgm-1s-2.

Dimension of Pressure is, [ML-1T-2]

Example of Pressure in Real Life

  • While cutting fruit or a vegetable, a sharp knife is used instead of a blunt one so that the pressure applied on the fruit is more and the fruits cut easily.
  • The nails that are nailed on the wall are very pointy at the end in order to put more pressure on the wall.
  • Porters put a round piece of cloth on their heads in order to increase the area and the pressure is less so that heavyweights can be applied.
Example of Pressure in Real Life

 

Types Of Pressure

We can easily classified pressure into different categories that include,

  • Absolute Pressure
  • Gauge Pressure
  • Differential Pressure
  • Sealed Pressure or Vacuum Pressure

There are different types of Pressure, and they have different units of pressure. For instance, atm is the unit used for atmospheric pressure. Let’s take a look at the different types of Pressure present,

Ambient Pressure

 It is defined as the pressure applied to an object because of its surroundings including liquid, gases, and other variables.

Atmospheric Pressure

Air is present above the sea level, the pressure exerted by the air in the atmosphere is known as atmospheric pressure. The unit used for measuring the atmospheric pressure is atm. 

The human body also has Pressure inside the body which compensates for the pressure present in the atmosphere, Therefore, the Human body does not feel it. The atmospheric pressure varies due to the fluctuation in the atmosphere. The weight of air is responsible for the atmospheric pressure, and it is essential for life on Earth.

The instrument used to measure the atmospheric pressure is called Barometer. Barometer has Mercury filled, and it is vacuumed in the rest of the space. It measures Patm as pgh

Patm = pgh

Where, 

  • p is the density of the air
  • g is the acceleration due to gravity
  • h is the height of the mercury

Absolute Pressure

Absolute Pressure is the pressure with respect to Zero pressure present, that is, with respect to no pressure present in the empty, free space. No pressure is obtained in a vacuum. Absolute pressure is denoted as Pabs

Differential Pressure

Differential Pressure, as the name suggests, is the difference between the two values of pressure. The pressure obtained will be lesser than either of the pressures and the unit is the same for the differential pressure obtained.

Pd = P2 – P1

Gauge Pressure

Gauge pressure is also known as Overpressure, and it is the recently invented pressure. The differential pressure obtained from atmospheric pressure and absolute pressure is known as overpressure or gauge pressure.

Below given figure shows the particular relation among Gauge Pressure, Absolute Pressure, Atmospheric pressure,

Gauge Pressure

 

Note: In order to measure Blood pressure, an inflatable cuff is placed on the forearm, Blood flow is detected and the corresponding pressures are measured in the mercury- filled manometer (Device used to measure pressure). The maximum blood pressure is called as Systolic Pressure. The minimum blood pressure is called as Diastolic pressure.

Sealed Pressure

The vacuum is a space where the absolute pressure is zero. Perfect vacuum condition is difficult to achieve practically and is only a theoretical value. When the pressure is lower than the atmospheric pressure vacuum is created. Practically, the vacuum will only be partially achieved and is known as the partial vacuum. A high vacuum means that the absolute pressure is very low.

The pressure is measured with reference to a sealed chamber closed with atmospheric pressure. The sealed sensor is used to measure the sealed pressure and is made of a sensing element that is sealed to make it air-tight and avoid further changes in the pressure due to changes in atmospheric conditions. Sealed pressure is used to protect pressure transducers from damage.

Vacuum Pressure

The pressure which is calculated below the atmospheric pressure is known as vacuum pressure. Hence, the negative value of the gauge pressure is the vacuum pressure.

Read More,

Solved Example on Pressure

Example 1: The mass of an object is 50 kgs and the object is accelerating at 2 m/sec2. This object strikes a surface of area 5 m2. Find the pressure exerted by the object on the surface.

Solution:

Given

  • Mass = 50kgs
  • Acceleration (a)= 2 m/sec2
  • Area of surface (A) = 5 m2

Using force formula,

Force (F) = Mass × Acceleration

F = 50 × 2

F= 100 N

Now using the Pressure formula as,

P = F/A

P = 100/5

P = 20 Nm-2

The, pressure exerted by object o surface the surface is, 20 Nm-2

Example 2: An object is being pushed with a force of 50N and the base of the object is 10m2, What will be the pressure exerted by the object on the surface?

Solution: 

Given,

  • Force = 50 N
  • Area = 10 m2

Pressure = Force/Area

P = 50/10

P = 5 N/m2

Thus, the pressure applied on the object is, 5 N/m2

Example 3: An object exerted a pressure of 10N/m2, and the area for which the pressure is applied is 30m2. Find the amount of Force required.

Solution:

Given: 

  • Pressure (P) = 10N/m2
  • Area (A) = 30m2

We know that, 

P = F/A

F = P × A

F = 10 × 30 = 300 N

Thus, the force exerted by the object is, 300 N.

FAQs on Types Of Pressure

Q1: What is Pressure?

Answer:

The pressure is defined as the force applied on an object measured per unit area, i.e. the force applied per unit area of the object is called the pressure of the object.

Q2: What is Pressure Formula?

Answer:

The formula used to calculate the pressure applied on an object is,

P = F/A

where,
F is the force applied
A is the area of the surface on which force is applied

Q2: What is Unit and Dimension of Pressure?

Answer:

We can calculate the pressure applied on an object by taking the ratio of force applied to the surface area of the object. So the force is measured in kgms2. The SI unit to measure pressure is Pascal (Pa). The dimension of pressure is,[ML-1T-2]

Q3: What are Different Types of Pressure?

Answer:

The different types of pressure experienced by us,

  • Absolute Pressure
  • Gauge Pressure
  • Differential Pressure
  • Sealed Pressure or Vacuum Pressure

Q4: What is difference between Gauge Pressure and Differential Pressure?

Answer:

Differential Pressure is the difference between the two pressure while Gauge Pressure or Overpressure is defined as the difference between Absolute Pressure and Atmospheric Pressure. 

Therefore, we can conclude that Gauge Pressure can be Differential Pressure but not vice-versa.

Q5: Why Straps Provided on School Bags are made Wider?

Answer:

The straps provided in the school bag are made wider so as to reduce the pressure exerted by the school bag on the shoulders of the children. As increasing the surface area of the straps reduces the pressure applied by the bag,

Pressure is inversely proportional to the surface area of the object.

P ∝ 1/A



Last Updated : 04 Feb, 2024
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