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 ↓


Pascal's law and its applications


Understanding the principles of how matter behaves is an important part of physics, especially when it comes to density and pressure. A fundamental law that describes how pressure is transmitted in fluids is Pascal's law. Named after French mathematician and physicist Blaise Pascal, this law forms the basis for many of the technologies we use in everyday life.

What is Pascal's law?

Pascal's law, also called Pascal's principle, states that "a pressure change applied to a closed fluid is transmitted without diminution to every point in the fluid and to the walls of its container." This means that any change in pressure at any point in a closed fluid is felt throughout the fluid.

Understanding Pascal's law: The basics of pressure

Pressure is defined as force per unit area. It is a measure of how much force is acting on a certain area. Imagine you have a container full of water and you apply pressure to a piston, the pressure you apply is evenly distributed throughout the water and is exerted on all parts of the container.

P = frac{F}{A}

Where:

  • P is the pressure
  • F is the applied force
  • A is the area over which the force is applied

Visual example

Imagine a simple system where you have a container filled with liquid and two pistons of different sizes.

Piston A Piston B

Piston A is smaller than piston B. If you apply force to piston A, the pressure is transmitted evenly throughout the fluid to piston B. As a result, even though piston B is larger, it can exert more force because the pressure is constant, and piston B has a larger area. This is the basic operating principle behind hydraulic systems.

Applications of Pascal's law

The principle of transmitted pressure is applied in many devices and technologies. Let's explore some common applications:

1. Hydraulic system

The most common application of Pascal's law is in hydraulic systems. These systems use incompressible fluids to transmit force from one location to another. Examples of hydraulic systems include car brakes, hydraulic lifts, and jacks.

Car brakes

Hydraulic brakes in cars work using Pascal's law. When you press the brake pedal, a piston compresses a fluid that transfers pressure through lines to another set of pistons on the wheel brakes. This pressure multiplies, applying force to stop the car.

Simple car brake system

Pedal wheel

Converting the pedal force applied to stop the wheels into more force is a practical demonstration of Pascal's law.

2. Hydraulic lift

Hydraulic lifts take advantage of Pascal's law to lift heavy objects. These lifts produce a large force over a large area by applying a small force over a small area. This is commonly seen in garages and elevators.

Example calculation

Consider a hydraulic lift that has a small piston with an area of 1 m2 and a large piston with an area of 10 m2. If a force of 100 N is applied to the small piston, we can calculate the force exerted by the large piston.

F_1 = 100 text{ N}, A_1 = 1 text{ m}^2, A_2 = 10 text{ m}^2
    text{Pressure remains constant, hence: }
    frac{F_1}{A_1} = frac{F_2}{A_2}
    frac{100}{1} = frac{F_2}{10}
    F_2 = 100 times 10 = 1000 text{ N}

Therefore, the lift can exert a force of 1000 N using only 100 N input force.

3. Hydraulic press

The hydraulic press is another common device that uses Pascal's law. It is used to compress materials, mold objects, and crush cars in junkyards. This device uses a small amount of force to produce a lot of force.

Hydraulic press working illustration

Small piston Big piston

As in elevators, a small input force can be converted into a very large output force through pressure transmission.

4. Syringe

Syringes in the medical field apply Pascal's law to inject and remove fluids in the body. When the plunger of the syringe is pressed, the pressure applied to the fluid inside is transmitted evenly throughout the fluid.

Syringe apparatus

Rider Needle

Applying pressure to the plunger forces the fluid out evenly through the needle.

Conclusion

Pascal's law is a fundamental principle in physics that describes how fluids behave under pressure. This principle is applied extensively in a variety of machines and devices, making tasks more efficient and making it possible to manipulate large forces with minimal effort. Understanding Pascal's law provides insight into the simple yet powerful mechanics that form the basis of technologies that play essential roles in the industrial, automotive, and medical sectors.


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Pressure in solids, liquids and gases
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Pascal's law and its applications

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