Grade 11
  1. Mechanics  1.1. dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two and three dimensions  1.1.3. Displacement and Distance  1.1.4. Speed and Velocity  1.1.5. Acceleration and deceleration  1.1.6. Graphical analysis of motion  1.1.7. Equations of motion (advanced derivations)  1.1.8. Free fall and terminal velocity  1.1.9. Projectile motion  1.1.10. Relative velocity in one and two dimensions  1.1.11. Motion of a car on an inclined plane  1.2. Dynamics  1.2.1. Newton's laws of motion and their applications  1.2.2. Inertia and Newton's first law  1.2.3. Force and types of force  1.2.4. Static and kinetic friction  1.2.5. Circular motion and centripetal acceleration  1.2.6. Non-uniform circular motion  1.2.7. Banking of roads and curves  1.2.8. Momentum and Impulse  1.2.9. Conservation of momentum in one and two dimensions  1.2.10. Applications of Newton's Third Law  1.3. Work, Energy and Power  1.3.1. Work done by a constant and variable force  1.3.2. Work–energy theorem  1.3.3. Kinetic and potential energy  1.3.4. Gravitational and elastic potential energy  1.3.5. Conservation of mechanical energy  1.3.6. Power and instantaneous power  1.3.7. Efficiency of machines  1.3.8. Work done by conservative and non-conservative forces  1.4. Rotational motion  1.4.1. Torque and angular acceleration  1.4.2. Rotational equilibrium  1.4.3. Moment of inertia and its applications  1.4.4. Angular momentum and its conservation  1.4.5. Kinetic energy of rolling motion and rotation  1.4.6. Parallel and Perpendicular Axis Theorem  1.4.7. Dynamics of rotational motion
  2. Gravitational force  2.1. Universal gravitation  2.1.1. Newton's law of universal gravitation  2.1.2. Gravitational field and potential  2.1.3. Change in acceleration due to gravity  2.1.4. Kepler's laws of planetary motion  2.1.5. Orbital mechanics and satellites  2.1.6. Escape velocity and orbital velocity  2.1.7. Weightlessness and free fall  2.1.8. Gravitational potential energy and energy in orbits  2.1.9. Black holes and gravitational lensing
  3. Properties of matter  3.1. Fluid mechanics  3.1.1. Density and pressure in liquids  3.1.2. Pascal's theory and applications  3.1.3. Archimedes' Principle and Buoyancy  3.1.4. Bernoulli's equation and applications  3.1.5. Continuity equation and the Venturi effect  3.1.6. Surface tension and capillarity  3.1.7. Viscosity and Poiseuille's Law  3.1.8. Reynolds number and turbulence  3.2. Elasticity and deformation  3.2.1. Hooke's law and the stress-strain relation  3.2.2. Elastic modulus and applications  3.2.3. Deformation and yield strength of solids
  4. Thermal physics  4.1. Heat and temperature  4.1.1. Thermometric properties and temperature scale  4.1.2. Thermal expansion of solids, liquids and gases  4.1.3. Heat transfer system  4.1.4. Specific heat capacity and calorimetry  4.1.5. Latent heat and phase change  4.2. Kinetic theory of gases  4.2.1. Molecular model of gases  4.2.2. Kinetic explanation of temperature  4.2.3. Ideal Gas Equation and Deviations  4.2.4. Mean free path and Maxwell–Boltzmann distribution  4.3. Laws of Thermodynamics  4.3.1. Zeroth Law and Thermal Equilibrium  4.3.2. First Law and Internal Energy  4.3.3. The Second Law and Entropy  4.3.4. Carnot cycle and heat engines  4.3.5. Refrigerators and heat pumps
  5. Waves and oscillations  5.1. Simple Harmonic Motion  5.1.1. Equations of SHM  5.1.2. Energy in SHM  5.1.3. Damped and forced oscillations  5.1.4. Resonance and applications  5.1.5. Pendulum and spring-mass system  5.2. Wave motion  5.2.1. Types of mechanical waves  5.2.2. Wave motion and energy transport  5.2.3. Superposition Principle and Standing Waves  5.2.4. Reflection, Refraction and Diffraction  5.2.5. Doppler effect in sound and light  5.2.6. Pulsations and interference
  6. Electricity and Magnetism  6.1. Electrostatics  6.1.1. Electric charge and conservation  6.1.2. Coulomb's law and its applications  6.1.3. Electric field and electric flux  6.1.4. Electric potential and potential energy  6.1.5. Capacitance and Energy Stored in a Capacitor  6.2. Current Electricity  6.2.1. Ohm's law and electrical resistance  6.2.2. Resistivity and temperature dependence  6.2.3. Kirchhoff's Laws and Circuit Analysis  6.2.4. Electrical power and efficiency  6.2.5. Combination of resistors  6.3. Magnetism and Electromagnetism  6.3.1. Magnetic fields and their sources  6.3.2. Magnetic force on moving charges  6.3.3. Electromagnetic induction  6.3.4. Faraday's and Lenz's laws  6.3.5. Inductance and Transformer  6.3.6. Alternating current and its applications
  7. Optics  7.1. Reflection and Refraction  7.1.1. laws of reflection and refraction  7.1.2. Mirrors and lenses  7.1.3. Total internal reflection and optical fiber  7.2. Wave optics  7.2.1. Interference and Diffraction  7.2.2. Young's double-slit experiment  7.2.3. Polarization of light
  8. Modern Physics  8.1.1. Photoelectric effect and Einstein's theory  8.1.2. Wave–particle duality  8.1.3. Heisenberg's uncertainty principle  8.1.4. Compton Effect  8.2. Atomic and Nuclear Physics  8.2.1. Atomic model and energy levels  8.2.2. Radioactive decay and half-life  8.2.3. Nuclear Fission and Fusion
  9. Electronics and Communication  9.1. Semiconductors  9.1.1. pn junction and diode  9.1.2. Transistors and Logic Gates  9.1.3. Integrated Circuits and Applications  9.2. Communication Systems  9.2.1. Basics of Analog and Digital Communication  9.2.2. Wireless and Optical Communication  9.2.3. Modulation and Demodulation

Grade 11 → Properties of matter → Fluid mechanics ↓


Archimedes' Principle and Buoyancy


Archimedes' principle and the concept of buoyancy are important to understanding how objects behave when immersed in a fluid. This principle explains why objects float, sink, or remain neutrally buoyant depending on the density of the fluid and the object's own density. In this journey through fluid mechanics, we will explore these concepts in detail, providing both text and visual examples to aid understanding.

Understanding liquids

Before we can understand Archimedes' principle, we need to understand what fluids are. In physics, the term "fluid" refers to any substance that can flow, including liquids and gases. Unlike solids, fluids have no fixed shape; instead, they take the shape of their container.

What is buoyancy?

Buoyancy is the upward force that fluids exert on objects that are immersed in them. This force is what makes objects seem lighter in water than in air. The concept of buoyancy is important in designing ships, submarines, and even hot air balloons.

Archimedes principle

The Archimedes principle is named after the ancient Greek mathematician and inventor Archimedes. It states:

"An object immersed in a fluid experiences an upward buoyant force equal to the weight of the fluid it displaces."

This principle can be expressed mathematically using the following formula:

F_b = ρ_fluid × V_displaced × g

Where:

  • F_b = buoyancy force
  • ρ_fluid = density of fluid
  • V_displaced = volume of fluid displaced by the object
  • g = acceleration due to gravity

This formula helps us understand how various factors such as density and volume of the fluid affect the buoyancy force experienced by an object.

Visualization of the bounce

Let's see how buoyancy works with a simple example of a block submerged in water:

Water block buoyant force

In this picture, the orange block is partially submerged in blue water. The red arrow pointing upward shows the buoyancy force acting on the block.

Why do objects float, sink or hang?

Whether an object floats, sinks, or floats in a fluid depends on its density relative to the density of the fluid.

Float

If the density of an object is less than the density of the fluid it will float. For example, consider a piece of wood in water. The density of wood is less than that of water, so it floats.

Drown

If the density of an object is greater than the density of the fluid it will sink. A rock placed in water will sink because it is denser than water.

Stay suspended

If the density of an object is equal to the density of the fluid it will stay suspended in the fluid. A fish can stay suspended in water by adjusting its buoyancy.

Equilibrium is maintained when the weight of the fish (the downward force) is equal to the buoyancy force (the upward force).

Practical applications of buoyancy

The principle of buoyancy is used in a variety of practical applications:

Ships and boats

Ships and boats are designed based on the principles of buoyancy. By controlling the shape and volume of the hull, ships can displace enough water to create enough buoyancy force to support heavy loads.

Submarines

Submarines adjust their buoyancy by controlling the entry of water into their ballast tanks. By filling these tanks with water, the submarine can sink. To rise, water is pumped out, reducing the overall density.

Balloons

Hot air balloons float in the air because of buoyancy. The hot air inside the balloon is less dense than the cold air outside, creating an upward buoyancy force that helps the balloon rise.

Experiments with buoyancy

Doing simple experiments can help you understand buoyancy better. Here are some activities:

Floating and sinking with mud

Make different shapes using modelling clay and submerge them in water. Observe how the shape affects buoyancy. Try to make a shape that floats and explain your observation.

Layered fluid

Fill a transparent container with liquids of different densities, such as oil, water, syrup or honey. Drop small objects into the container and see which layer they settle into. This experiment sheds light on how different densities affect buoyancy.

Summary

Understanding Archimedes' principle and buoyancy is important for understanding how different objects interact with fluids. This principle not only explains why objects float or sink, but also plays an important role in shipbuilding, diving, and aviation. By experimenting and observing real-life examples, the concepts of buoyancy become more tangible and relevant.


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Archimedes' Principle and Buoyancy

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