Grade 10
  1. Mechanics  1.1. Dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two dimensions  1.1.3. Displacement and Distance  1.1.4. Speed and Velocity  1.1.5. Acceleration  1.1.6. Graphical representation of motion  1.1.7. Equations of motion  1.1.8. Free fall and acceleration due to gravity  1.1.9. Projectile motion  1.1.10. Relative speed  1.2. Dynamics  1.2.1. Newton's Laws of Motion  1.2.2. Inertia and mass  1.2.3. Force and its types  1.2.4. action and reaction force  1.2.5. Friction and its effects  1.2.6. Coefficient of friction  1.2.7. Circular motion  1.2.8. Centripetal force and centripetal acceleration  1.2.9. Momentum and Impulse  1.2.10. Conservation of momentum  1.2.11. Newton's third law and applications  1.3. Work, Energy and Power  1.3.1. Work done by the force  1.3.2. Work–energy theorem  1.3.3. Kinetic energy  1.3.4. Potential energy  1.3.5. Mechanical energy  1.3.6. Energy Conservation  1.3.7. Power and efficiency  1.3.8. Renewable and non-renewable energy sources  1.4. Gravitational force  1.4.1. Newton's law of universal gravitation  1.4.2. Gravitational field and field strength  1.4.3. Acceleration due to gravity on different planets  1.4.4. Kepler's laws of planetary motion  1.4.5. Orbits and satellites  1.4.6. Weight and apparent weight  1.4.7. Gravitational potential energy
  2. Properties of matter  2.1. States of matter  2.1.1. Solid, liquid and gas  2.1.2. Molecular structure of matter  2.1.3. Intermolecular forces  2.1.4. Plasma and Bose–Einstein condensate  2.2. Pressure  2.2.1. Definition of Pressure  2.2.2. Pressure in liquids  2.2.3. Atmospheric pressure  2.2.4. Pascal's principle  2.2.5. Archimedes' Principle and Buoyancy  2.2.6. Surface tension and capillarity  2.3. Elasticity  2.3.1. Hooke's law  2.3.2. Stress and strain  2.3.3. Elastic Limit and Modulus of Elasticity  2.3.4. Applications of Elasticity
  3. Thermal physics  3.1. heat and temperature  3.1.1. Difference Between Heat and Temperature  3.1.2. Temperature scale  3.1.3. Thermal expansion  3.1.4. Thermal equilibrium  3.2. Heat transfer  3.2.1. Conductivity  3.2.2. Convection  3.2.3. Radiation  3.2.4. Insulation and its applications  3.3. Thermal properties of matter  3.3.1. Specific heat capacity  3.3.2. Latent heat and phase change  3.3.3. Boiling and Melting Point  3.3.4. Heat engines and refrigeration  3.4. Laws of Thermodynamics  3.4.1. Zeroth law of thermodynamics  3.4.2. First law of thermodynamics  3.4.3. Second law of thermodynamics  3.4.4. Carnot cycle
  4. Waves and optics  4.1. Nature and properties of waves  4.1.1. Types of waves in nature and properties of waves  4.1.2. Transverse and longitudinal waves  4.1.3. Wave parameters  4.1.4. Reflection and refraction of waves  4.1.5. Superposition and Interference  4.1.6. Standing Waves and Resonance  4.1.7. Doppler effect  4.2. Sound waves  4.2.1. Characteristics of sound waves  4.2.2. Speed of sound in different mediums  4.2.3. Applications of sound waves  4.2.4. Ultrasound and its uses  4.3. Light Waves and Optics  4.3.1. Nature of light  4.3.2. Reflection of light  4.3.3. Laws of reflection  4.3.4. Mirrors and Image Formation  4.3.5. Refraction of light  4.3.6. Snell's Law  4.3.7. Lenses and Image Formation  4.3.8. Total internal reflection and critical angle  4.3.9. Optical fibre  4.4. Optical Instruments  4.4.1. Microscope  4.4.2. Telescope  4.4.3. Human eye and vision defects  4.4.4. Camera and its working principle
  5. Electricity and Magnetism  5.1. Electrostatics  5.1.1. Electric charge and its properties  5.1.2. Conductors and Insulators  5.1.3. Coulomb's law  5.1.4. Electric field and field lines  5.1.5. Electric potential and potential difference  5.1.6. Capacitors and Capacitance  5.2. Current Electricity  5.2.1. Electric current and its measurement  5.2.2. Ohm's law  5.2.3. Resistance and resistivity  5.2.4. Series and Parallel Circuits  5.2.5. Electric power and energy  5.2.6. Kirchhoff's Laws  5.3. Magnetism and Electromagnetism  5.3.1. Magnetic field and field lines  5.3.2. Magnetic effects of electric current  5.3.3. Electromagnetic induction  5.3.4. Faraday's laws of electromagnetic induction  5.3.5. Transformers and Applications  5.3.6. AC and DC current
  6. Modern Physics  6.1. Nuclear physics  6.1.1. Structure of the atom  6.1.2. Bohr's atomic model  6.1.3. Electron Energy Levels  6.1.4. X-rays and applications  6.2. Radioactivity  6.2.1. Types of radiation  6.2.2. Half-life and radioactive decay  6.2.3. Nuclear reactions and applications  6.2.4. Fission and Fusion  6.3. Quantum physics  6.3.1. Wave–particle duality  6.3.2. Photoelectric effect  6.3.3. Energy quantization  6.3.4. Heisenberg's uncertainty principle
  7. Electronics and Communication  7.1. Semiconductors  7.1.1. Conductors, Insulators and Semiconductors  7.1.2. Diodes and their applications  7.1.3. Transistors and Logic Gates  7.1.4. LEDs and photodiodes  7.2. Communication Systems  7.2.1. Basics of communication  7.2.2. Analog and digital signals  7.2.3. Wireless and optical fibre communication  7.2.4. Radio Waves and Modulation

Grade 10 → Properties of matter → Pressure ↓


Atmospheric pressure


Atmospheric pressure is a fundamental concept in the study of physics, particularly in the properties of matter. To understand this concept, it is important to understand what pressure is. Pressure is defined as the force exerted per unit area on the surface of an object. As for atmospheric pressure, it applies to the pressure exerted by the weight of the Earth's atmosphere above a specific point.

Withstanding the pressure

Let's start by discussing what pressure means in general. Imagine you have a small object in your hand, such as a book, that you are holding. The book exerts a force on your hand because of its weight. The part of your hand that is in contact with the book experiences this force.

The mathematical expression for pressure is:

Pressure (P) = Force (F) / Area (A)

In the case of the book, if the weight of the book is 10 newtons and the area of the book in contact with your hand is 0.5 square meter, then the pressure exerted on your hand is:

P = 10 N / 0.5 m² = 20 N/m²

Atmospheric pressure around us

Atmospheric pressure, sometimes also referred to as air pressure, is the force exerted by the atmosphere due to the Earth's gravitational pull on air molecules. Our atmosphere is a layer of gases surrounding the Earth, and these gases are freely moving particles that produce pressure through collisions with surfaces.

To visualize atmospheric pressure, imagine that the Earth is covered by a vast ocean of air. This ocean exerts a downward force on everything within it, including you!

atmospheric pressure

Simply put, atmospheric pressure is the weight of air pressing down on a surface from above. Since air is heavy, the pressure exerted is also significant.

Standard atmospheric pressure

Standard atmospheric pressure at sea level is defined as 101,325 pascals (Pa). This is equal to 1 atmosphere (atm), 760 millimeters of mercury (mmHg), which is the traditional way of measuring pressure using a mercury barometer.

You can express standard atmospheric pressure in a variety of units:

  • 1 atmosphere (atm)
  • 101,325 pascal (Pa)
  • 760 millimeters of mercury (mmHg)
  • 14.696 pounds per square inch (psi)

Measuring atmospheric pressure

Atmospheric pressure is typically measured using a barometer. A simple barometer can be made using a column of mercury. As atmospheric pressure changes, it causes the mercury to rise or fall. A higher mercury column indicates higher atmospheric pressure and vice versa.

Mercury barometer

In a mercury barometer the atmospheric pressure balances a column of mercury, and the height of the column of mercury is an indication of atmospheric pressure. This is because the pressure exerted by the weight of the column of mercury is balanced by the atmospheric pressure.

Mercury Basement

In this example, the pressure exerted by a column of mercury is calculated by taking into account the height of the column and the density and gravity of mercury.

Factors affecting atmospheric pressure

There are many factors that affect atmospheric pressure. These include:

  • Altitude: As you go higher above sea level, atmospheric pressure decreases because there is less air above you. Consider a mountaineer who is climbing to a higher altitude. They experience less atmospheric pressure.
  • Temperature: Air molecules move faster as the temperature increases, causing them to spread apart, which can lower atmospheric pressure. Conversely, cooling air molecules slows them down and brings them closer together, which increases atmospheric pressure.
  • Weather patterns: High pressure and low pressure systems in the atmosphere create different weather patterns. In a high pressure area, the air is denser and is usually associated with clear skies. In contrast, low pressure areas often bring clouds and precipitation.

Effects of atmospheric pressure

Atmospheric pressure has an impact on our daily lives in many ways. For example, it plays an important role in weather forecasting. Understanding and predicting changes in atmospheric pressure helps meteorologists predict possible weather conditions.

Boiling point of water

The boiling point of water is affected by atmospheric pressure. At higher altitudes, where atmospheric pressure is lower, water boils at a lower temperature. This is why cooking instructions often need to be adjusted for higher altitudes.

Breathing

The process of breathing depends on pressure differences. When you breathe in, your lungs expand, creating a pressure difference between the air inside your lungs and atmospheric pressure, causing air to flow into the lungs. When you exhale, the pressure inside your lungs becomes greater than atmospheric pressure, causing air to flow out.

Closing thoughts

Atmospheric pressure is an essential aspect of physics that affects a variety of daily activities and natural phenomena. Understanding atmospheric pressure and its measurement not only enhances our understanding of weather conditions but also helps in engineering applications. Through a basic knowledge of how atmospheric pressure works, students and learners can appreciate the world around them and its subtle effects on their environment.


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Atmospheric pressure

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