Grade 9
  1. Mechanics  1.1. Motion  1.1.1. Types of motion  1.1.2. Distance and displacement  1.1.3. Speed and Velocity  1.1.4. Acceleration  1.1.5. Graphical representation of motion  1.1.6. Equations of motion  1.1.7. Uniform and non-uniform motion  1.1.8. Free fall and acceleration due to gravity  1.1.9. Relative speed  1.1.10. Circular motion  1.2. Laws of force and motion  1.2.1. The concept of force  1.2.2. newton's first law of motion  1.2.3. Newton's second law of motion  1.2.4. Newton's third law of motion  1.2.5. Inertia and types of inertia  1.2.6. Motion  1.2.7. Conservation of momentum  1.2.8. Application of Newton's laws in daily life  1.2.9. Types of Forces (Contact and Non-Contact)  1.2.10. Friction and its effects  1.3. Gravitational force  1.3.1. Newton's law of universal gravitation  1.3.2. Importance of Gravitational Force  1.3.3. Acceleration due to gravity  1.3.4. Free fall and weightlessness  1.3.5. Mass and weight  1.3.6. Variation of g with height and depth  1.3.7. Kepler's laws of planetary motion  1.3.8. Satellites and their orbits  1.4. Work, Energy and Power  1.4.1. Concept of work  1.4.2. Positive and negative actions  1.4.3. Work done by constant and variable force  1.4.4. Energy and its forms  1.4.5. Kinetic energy and potential energy  1.4.6. Law of conservation of energy  1.4.8. Commercial unit of energy  1.4.9. Work–energy theorem  1.5. Simple machines  1.5.1. Types of simple machines  1.5.2. Mechanical advantage  1.5.3. Machine efficiency  1.5.4. Levers and their types  1.5.5. Pulleys and Inclined Planes  1.5.6. Gears and their uses
  2. Properties of matter  2.1. States of matter  2.1.1. Solids, liquids and gases  2.1.2. Properties of different states of matter  2.1.3. Change in state of matter  2.1.4. Plasma and Bose–Einstein condensate  2.2. Density and pressure  2.2.1. Concept of density and relative density  2.2.2. Pressure in solids, liquids and gases  2.2.3. Pascal's law and its applications  2.2.4. Atmospheric pressure and its variations  2.2.5. Surface tension and capillarity  2.3. Buoyancy and Archimedes' principle  2.3.1. Buoyant force  2.3.2. Archimedes principle  2.3.3. Applications of Archimedes' Principle  2.3.4. floating and sinking objects  2.3.5. Theory of Flotation and Archimedes' Principle
  3. Heat and Thermodynamics  3.1. Temperature and heat  3.1.1. Concept of heat and temperature  3.1.2. Temperature measurement  3.1.3. Temperature scales  3.2. Heat transfer  3.2.1. Conduction of heat  3.2.2. Convection of heat  3.2.3. heat radiation  3.2.4. Applications of heat transfer  3.2.5. Thermal conductivity  3.3. Thermal expansion  3.3.1. Expansion of solids, liquids and gases  3.3.2. Abnormal expansion of water  3.3.3. Applications of Thermal Expansion  3.4. Specific heat capacity and latent heat  3.4.1. Concept of specific heat capacity  3.4.2. Measurement and applications of specific heat  3.4.3. Latent heat of fusion and vaporization  3.4.4. Heat Engines and Efficiency
  4. Waves and sound  4.1. Waves and their types  4.1.1. Mechanical and electromagnetic waves  4.1.2. Longitudinal and Transverse Waves  4.1.3. Properties of Waves  4.1.4. Wavelength, frequency and speed of the wave  4.1.5. Superimposition of waves  4.2. Sound waves  4.2.1. Nature and transmission of sound  4.2.2. Speed of sound in different mediums  4.2.3. Reflection of sound and echo  4.2.4. Sonar and ultrasound  4.2.5. Resonance and pulsation  4.3. Sound characteristics  4.3.1. Intensity, loudness and quality of sound  4.3.2. Doppler effect in sound
  5. Lighting and Optics  5.1. Reflection of light  5.1.1. Laws of reflection  5.1.2. Reflection from a plane mirror  5.1.3. Reflection from a spherical mirror  5.1.4. Image formation by concave and convex mirrors  5.1.5. Applications of Reflection  5.2. Refraction of light  5.2.1. Laws of refraction  5.2.2. Refractive index  5.2.3. Refraction through a glass slab  5.2.4. Refraction in water and air  5.2.5. Lenses and their types  5.2.6. Image formation by convex and concave lenses  5.2.7. Total internal reflection and its applications  5.3. Dispersion and scattering of light  5.3.1. Spectrum of white light  5.3.2. Prisms and Dispersion  5.3.3. Tyndall effect and blue sky
  6. Electricity and Magnetism  6.1. Electric charge and static electricity  6.1.1. The concept of electric charge  6.1.2. Charging by friction, contact and induction  6.1.3. Electroscope and its working  6.2. Current Electricity  6.2.1. The concept of electric current  6.2.2. Ohm's Law and Resistance  6.2.3. Factors affecting resistance  6.2.4. Series and Parallel Circuits  6.2.5. Heating effect of electric current  6.2.6. Electric power and energy  6.3. Magnetism  6.3.1. Natural and artificial magnets  6.3.2. Properties of magnets  6.3.3. Earth's magnetism  6.3.4. Magnetic field and field lines  6.3.5. Electromagnets and their applications
  7. Modern Physics  7.1. structure of the atom  7.1.1. Atomic Structure and Subatomic Particles  7.1.2. Electrons, Protons, and Neutrons  7.1.3. Rutherford and Bohr model  7.2. Radioactivity  7.2.1. Types of radioactive emissions  7.2.2. Half-life and radioactive decay  7.2.3. Uses and Hazards of Radioactivity
  8. Space science and astronomy  8.1. The universe and its components  8.1.1. Stars and galaxies  8.1.2. Planets and Solar System  8.2. Satellites  8.2.1. Natural and artificial satellites  8.2.2. Use of satellites

Grade 9 → Properties of matter ↓


Density and pressure


In the world of physics, it is very important to understand the properties of matter. This explanation will discuss two of these properties in depth: density and pressure. We will explore what they mean, how they relate to each other, and what real-world applications they have.

Density

Density is a measurement that tells us how much mass is contained in a given volume. Simply put, it is the mass per unit volume of a substance.

Formula of density

Density (ρ) = Mass (m) / Volume (V)

Where:

  • Density (ρ) is in kilograms per cubic meter (kg/m3)
  • Mass (m) in kilograms (kg)
  • Volume (V) is in cubic metres (m3)

Understanding density with an example

Imagine a box filled with marbles and another box of the same size filled with sand. The box containing marbles may be lighter than the box containing sand, even though they have the same volume. This is because the sand particles are more closely packed together, so they are denser than the marbles.

Visual example: density

Low Density High Density

Factors affecting density

The density of a substance can change under different conditions. Here are some factors:

  • Temperature: As the temperature of a substance increases, its volume generally increases while its mass remains constant, leading to a decrease in density.
  • Pressure: When pressure is applied to gases, their volume decreases, which increases their density.

Pressure

Pressure is defined as the force applied per unit area to the surface of an object. Understanding pressure is important because it plays a vital role in a variety of physical phenomena and applications.

Formula of pressure

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

Where:

  • Pressure (P) is in pascal (Pa)
  • Force (F) is in Newton (N)
  • Area (A) is in square metres (m2)

Understanding pressure with an example

Consider a scenario where you apply pressure to a wooden table with your palm. Now, apply the same force using the tip of a pencil. The tip of the pencil exerts much more pressure on the table than your palm because the area of contact is much smaller.

Visual example: pressure

Low Pressure High Pressure

Factors affecting pressure

The pressure exerted by a substance can be affected by several factors:

  • Area: If the area increases then the pressure applied by the same force also decreases.
  • Force: If force is applied on the same area then pressure also increases.
  • Height (in fluids): In fluids, pressure is also affected by the depth of the fluid column.

Pressure in liquids

Fluids exert pressure in all directions. The pressure in a fluid at a given depth depends largely on the density of the fluid and the height of the column of fluid above it.

Pressure (P) = Density (ρ) × Gravitational Field Strength (g) × Height (h)

Where:

  • Density (ρ) is in kilograms per cubic meter (kg/m3)
  • Gravitational field strength (g) is about 9.81 m/s2
  • Height (h) is in meters (m)

Real-world applications

Density applications

  • Shipbuilders: Consider the density of materials to make ships float.
  • Material selection: Engineers select materials based on density for specific purposes, such as selecting lightweight materials for aerospace design.

Pressure applications

  • Hydraulics: Pressure concepts are used in brakes, jacks, and other hydraulic machines.
  • Weather patterns: Meteorologists study air pressure patterns to predict the weather.

Both density and pressure play important roles in our everyday lives and technologies. Understanding these concepts allows us to use their properties in various technological, scientific, and industrial applications.


Grade 9 → 2.2


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Density and pressure

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