Archimedes' Principle
The fundamental law of buoyancy that explains why objects float or sink in fluids
The Principle Explained
Archimedes' Principle states that any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object. This principle explains why ships float, balloons rise, and why we feel lighter in water.
Discovered in the 3rd century BCE by Archimedes of Syracuse, this fundamental law of physics applies to all fluids, including liquids and gases.
Interactive Buoyancy Demonstration
What's happening: When the object's density is less than water (1 g/cm³), it floats. When it's greater, it sinks. At equal density, it achieves neutral buoyancy.
Practical Applications
Ship Design
Ensuring ships displace enough water to generate buoyant force equal to their weight, keeping them afloat.
Submarines
Using ballast tanks to change overall density, allowing submarines to dive and surface.
Swimming & Diving
Explaining why humans float and how buoyancy compensators help divers control their depth.
Hot Air Balloons
Hot air is less dense than surrounding cool air, creating buoyant force that lifts the balloon.
Hydrometers
Devices that measure liquid density by how deeply they sink into the fluid.
Medical Applications
Used in measuring body fat percentage through underwater weighing techniques.
Mathematical Formulation
Archimedes' Principle can be expressed mathematically to calculate the buoyant force acting on an object immersed in a fluid.
The magnitude of the buoyant force (F₆) is equal to the weight of the fluid displaced by the object. This depends on the density of the fluid (ρ), the volume of displaced fluid (V), and gravitational acceleration (g).
An object will float if its average density is less than the fluid's density, sink if greater, and remain suspended (neutral buoyancy) if equal.
Buoyant Force Formula
Where:
We will love to hear your thoughts — please share your comment on the blog post above!