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 → Buoyancy and Archimedes' principle ↓


Theory of Flotation and Archimedes' Principle


The principle of flotation and Archimedes' principle are fundamental concepts in physics that describe how an object behaves when it is placed in a fluid such as water or air. These concepts are important in understanding why objects float or sink and have many practical applications from shipbuilding to fluid measurement devices. Let's take a deeper look at each principle to see how they work and how they apply to real-life scenarios.

Understanding the surge

Buoyancy is the force exerted by a fluid that opposes the weight of an object. It acts in the upward direction, making objects immersed in a fluid seem lighter. The buoyancy force is the main reason objects float. To visualize buoyancy, imagine that you are holding a beach ball and trying to push it under the water in a swimming pool.

buoyant force weight

When you push the ball, you feel an upward force that pushes it back to the surface. This is the work of buoyancy. The buoyancy force must be equal to the weight of the fluid displaced by the object.

Archimedes principle

Archimedes' principle is named after the ancient Greek mathematician and physicist Archimedes, who stated that any object, whether fully or partially immersed in a fluid, is lifted by a force equal to the weight of the fluid displaced by the object. This principle helps explain why ships float and why hot air balloons rise.

To express Archimedes' principle mathematically:

Buoyant Force = Weight of Displaced Fluid

Suppose you have a steel cube of the same size and a wooden cube of the same size. When both are immersed in water, they displace the same amount of water. However, the steel cube experiences a lesser buoyancy force because it is denser and sinks, while the wooden cube can float because it is less dense.

Principle of Flotation

The principle of flotation states that a floating object displaces a weight of fluid equal to its own weight. This principle determines the behaviour of an object whether it floats or sinks.

For example, ships float because their design allows them to spread their weight over a volume, displacing a greater weight of water, even though the material (steel) is denser than water.

ship

Imagine a ship floating in the ocean. The buoyancy force is equal to the weight of the ship. The shape and hollow design causes it to displace enough water to balance the forces acting on it, which shows the principle of floating.

Examples and applications

1. Float the rubber duck

When you place a rubber duck in a bathtub filled with water, it floats. The weight of the rubber duck is balanced by the buoyancy force of the water it displaces. The material and shape of the duck allow it to displace enough water so that it floats.

2. Iceberg

Icebergs float on water because they are made of ice, which is less dense than liquid water. Typically, only 10% of an iceberg is visible above the water's surface, while the rest is submerged, illustrating Archimedes' principle.

Water

3. Hydrometer

A hydrometer is an instrument that measures the density or specific gravity of liquids. It floats in a liquid, and the point to which it sinks is related to the density of the liquid. This operation is a practical application of the principle of flotation.

Related calculations

These concepts come into play when calculating whether or not an object will float, or how much of a floating object will sink in water:

Density = Mass / Volume Buoyant Force = Volume of Fluid Displaced × Density of Fluid × Gravitational Acceleration (g)

For example, if a cylindrical object has uniform density and is floating in water, knowing the density of water and the volume of the object allows you to calculate how much of it will remain above the surface.

Conclusion

Understanding the theory of flotation and Archimedes' principle helps us figure out everyday phenomena and technological advancements, from designing large ships to understanding simple phenomena like ice floating on water. These principles illustrate the delicate balance of forces and densities that determine whether an object will rise, sink, or float. Using these principles helps engineers and scientists solve and innovate problems involving fluid dynamics.


Grade 9 → 2.3.5


U
username
0%
completed in Grade 9

← Prev (2.3.4)
floating and sinking objects
Next (3) →
Heat and Thermodynamics

Comments 



Theory of Flotation and Archimedes' Principle

https://www.physicsflow.com/g9/2.3.5?pfal=en