• NEET
      • Class 11th
      • Class 12th
      • Class 12th Plus
    • JEE
      • Class 11th
      • Class 12th
      • Class 12th Plus
    • Class 6-10
      • Class 6th
      • Class 7th
      • Class 8th
      • Class 9th
      • Class 10th
    • View All Options
      • Online Courses
      • Offline Courses
      • Distance Learning
      • Hindi Medium Courses
    • NEET
      • Class 11th
      • Class 12th
      • Class 12th Plus
    • JEE (Main+Advanced)
      • Class 11th
      • Class 12th
      • Class 12th Plus
    • JEE Main
      • Class 11th
      • Class 12th
      • Class 12th Plus
    • CUET
      • Class 12th
  • NEW
    • JEE MAIN 2025
    • NEET
      • 2024
      • 2023
      • 2022
    • Class 6-10
    • JEE Main
      • Previous Year Papers
      • Sample Papers
      • Result
      • Analysis
      • Syllabus
      • Exam Date
    • JEE Advanced
      • Previous Year Papers
      • Sample Papers
      • Mock Test
      • Result
      • Analysis
      • Syllabus
      • Exam Date
    • NEET
      • Previous Year Papers
      • Sample Papers
      • Mock Test
      • Result
      • Analysis
      • Syllabus
      • Exam Date
    • NCERT Solutions
      • Class 6
      • Class 7
      • Class 8
      • Class 9
      • Class 10
      • Class 11
      • Class 12
    • CBSE
      • Notes
      • Sample Papers
      • Question Papers
    • Olympiad
      • NSO
      • IMO
      • NMTC
    • ALLEN e-Store
    • AOSAT
    • ALLEN for Schools
    • About ALLEN
    • Blogs
    • News
    • Careers
    • Request a call back
    • Book home demo
NCERT SolutionsCBSE NotesCBSE Exam
Home
Science
Pressure

Pressure

What happens when you walk on soft snow or dry sand? Your feet sink into the snow or sand and walking can be difficult. If you ride a bicycle with narrow tyres over these surfaces, the tyres will sink even deeper than your feet. How deep you sink depends on your weight as well as the area over which you make contact with the sand or snow. For example, when you stand on snow with your normal shoes, you may sink deep into the soft snow [see figure (a)]. However, if you use special kinds of supports (or snow boards) having larger area than your shoes [see figure (b)], you can stand on the snow very easily.

Understanding pressure

In both cases, your weight exerted a downward force on the snow. What changed was the area of contact between you and the snow. By changing the area of contact, you changed the ‘pressure’ you exerted on the snow due to your weight. When you stood with supports
(or snow shoes), the area of contact increased, so that the same force was applied over a larger area. As a result, the pressure that was exerted on the snow decreased and you didn’t sink as deep.

Thrust

The force acting on an object perpendicular to the surface is called thrust.

Pressure

The thrust on unit area is called pressure.

Pressure=AreaThrust​=AreaForce​

1.0SI Unit of Pressure

N/m2 or N m–2. In honour of scientist Blaise Pascal, the SI unit of pressure is called "pascal", denoted as Pa.

1 Pascal = 1 Newton/(meter)2

or  1 Pa = 1 N/m2 = 1 N m–2

2.0Definition of 1 Pascal

If 1 newton force acts perpendicular to a surface of area 1m2, then the pressure acting on the surface is 1 pascal.

Pressure is a scalar quantity. Always remember it is the component of the force normal (perpendicular) to the area under consideration for calculating pressure, not the force vector.

A common unit of pressure is the atmosphere (atm), i.e. the pressure exerted by the atmosphere at sea level, 1 atm = 1.013 × 105 Pa

Another unit of pressure is bar, 1 Bar = 105 Pa

For a given force, pressure is inversely proportional to the area. Thus, the same force acting on a smaller area exerts a larger pressure, and a smaller pressure on a larger area.

The weight of a hundred rupee note resting completely flat on a table exerts a pressure of about 1 Pa on the table. Since 1 Pa is a very small unit of pressure, pressure sometimes is expressed in units of kPa (kilo pascal), which is 1,000 Pa.

Some more examples related to pressure

(1) You cannot cut vegetables with a blunt knife. But, if you use a sharp knife, it is quite easy to cut the vegetables. This is because the area of sharp edge of the knife is quite small and thus, pressure is large enough to cut the vegetables.

(2) The straps of shoulder bags are made wide (broad). This is because the wide straps have larger area so that the pressure exerted on the shoulder becomes quite small. Thus, it becomes quite comfortable to carry such shoulder bags.

(3) Porters (coolies) place on their heads a round piece of cloth, when they have to carry heavy load. By this they increase the area of contact of the load with their head. So, the pressure on their head is reduced and they find it easier to carry the load.

(4) Buildings have wide foundations so that they exert less pressure on the earth.

Solved Example

A block of wood is kept on a table top. The mass of the wooden block is 5 kg and its dimensions are 40 cm × 20 cm × 10 cm. Find the pressure exerted by the wooden block on the table top if it is made to lie on the table top with its sides of dimensions 

(a) 20 cm × 10 cm and (b) 40 cm × 20 cm (see figure, take g = 9.8 m/s2).

que

Solution

Given, mass of the wooden block, m = 5 kg

Thrust, F = weight of the wooden block = m × g = 5 × 9.8 = 49 N

(a) Area, A = 20 cm × 10 cm = 200 cm2 = 200 × 10–4 m2 = 0.02 m2 

Now, pressure, P = = = 2450 N m–2 

Now, pressure, P =AF​=0.0249​ = 2450 N m–2 

(b) Area, A = 40 cm × 20 cm = 800 cm2 = 800 × 10–4 m2 = 0.08 m2

Now, pressure,P=AF​=0.0849​ = 612.5 N m–2 

Thus, the pressure exerted by the face 20 cm × 10 cm is 2450 Nm–2 and by the face 40 cm × 20 cm is 612.5 Nm–2.

3.0Pressure in A Fluid

A fluid is any substance that has no definite shape and has the ability to flow. You might think of a fluid as being a liquid, such as water or motor oil, but gases are also fluids. When you are outside on a windy day, you can feel the air flowing past you because air can flow and has no definite shape, air is a fluid. Gases, liquids, and the state of matter called plasma, which is found in the Sun and other stars, are fluids and can flow. Fluids can exert pressure on the base and walls of the container in which they are enclosed.

4.0Also Read

Scattering of Light

Relative Density

Power of Accommodation

Work, Energy and Power

Buoyancy Force

Defects of Vision and Their Correction

Pascal’s law

Human Eye

Refraction of Light Through A Prism

Table of Contents


  • 1.0SI Unit of Pressure
  • 2.0Definition of 1 Pascal
  • 3.0Pressure in A Fluid
  • 4.0Also Read

Frequently Asked Questions

When you apply a force on the nail using a hammer with its head touching the wooden plank, the pressure exerted on the plank is quite small. This is because pressure is inversely proportional to area i.e., the larger the area, smaller the pressure on a surface for the same force. When you apply the same force on the nail with its pointed end touching the plank, pressure exerted on the plank is sufficient to insert it into the plank (see figure). This is because the area of the pointed end of the nail is much smaller than that of its head.

For a given force, as the area of contact increases, the pressure exerted decreases. Conversely, reducing the area increases the pressure because the same force is applied over a smaller area.

Join ALLEN!

(Session 2025 - 26)


Choose class
Choose your goal
Preferred Mode
Choose State
  • About
    • About us
    • Blog
    • News
    • MyExam EduBlogs
    • Privacy policy
    • Public notice
    • Careers
    • Dhoni Inspires NEET Aspirants
    • Dhoni Inspires JEE Aspirants
  • Help & Support
    • Refund policy
    • Transfer policy
    • Terms & Conditions
    • Contact us
  • Popular goals
    • NEET Coaching
    • JEE Coaching
    • 6th to 10th
  • Courses
    • Online Courses
    • Distance Learning
    • Online Test Series
    • NEET Test Series
    • JEE Test Series
    • JEE Main Test Series
    • CUET Test Series
  • Centers
    • Kota
    • Bangalore
    • Indore
    • Delhi
    • More centres
  • Exam information
    • JEE Main
    • JEE Advanced
    • NEET UG
    • CBSE
    • NCERT Solutions
    • NEET Mock Test
    • CUET
    • Olympiad
    • JEE Main 2 Solved Papers

ALLEN Career Institute Pvt. Ltd. © All Rights Reserved.

ISO