Glossary
Archimedes' Principle
A fundamental principle stating that the buoyant force on an object submerged or floating in a fluid is equal to the weight of the fluid displaced by the object.
Example:
A large cargo ship floats because it displaces a volume of water whose weight is exactly equal to the ship's total weight, as described by Archimedes' Principle.
Bernoulli's Principle
A principle stating that for an ideal fluid flowing horizontally, an increase in fluid speed occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy.
Example:
The curved shape of an airplane wing helps generate lift because faster air flow over the top creates lower pressure according to Bernoulli's Principle.
Buoyant Force
An upward force exerted by a fluid that opposes the weight of an object immersed in it, caused by the pressure difference between the top and bottom of the object.
Example:
A swimmer feels lighter in water because of the upward buoyant force exerted by the water.
Displaced Fluid
The volume of fluid that is pushed aside or moved out of the way by an object when it is immersed in that fluid.
Example:
When you drop an ice cube into a full glass of water, the water that spills over the rim is the displaced fluid.
External Forces (on fluids)
Forces acting on a fluid from outside its boundaries, such as gravity, pressure differences, or forces from solid surfaces, influencing the fluid's motion and shape.
Example:
A water wheel spins because the external forces of the flowing river push against its paddles.
Fluid Density
A measure of the mass per unit volume of a fluid, indicating how much mass is contained within a given space.
Example:
A hot air balloon rises because the heated air inside has a lower fluid density than the cooler air outside.
Fluid Dynamics
The branch of physics that studies how forces affect the motion of fluids, encompassing both the microscopic interactions of particles and the macroscopic behavior of the fluid.
Example:
Designing the aerodynamic shape of a race car involves extensive study of fluid dynamics to minimize air resistance.
Internal Interactions (in fluids)
Forces and energy exchanges occurring between individual particles within a fluid, which contribute to properties like pressure, viscosity, and flow patterns.
Example:
The stickiness of honey is a direct result of strong internal interactions between its sugar and water molecules.
Laminar Flow
A type of fluid flow characterized by smooth, parallel layers of fluid moving without significant mixing or turbulence.
Example:
When a faucet is barely turned on, the water often flows out in a smooth, glass-like stream, demonstrating laminar flow.
Newton's Laws of Motion
Fundamental principles describing how forces affect the motion of objects, which also apply to individual fluid particles experiencing forces and accelerations.
Example:
When a strong current pushes a tiny water droplet, its change in velocity is governed by Newton's Laws of Motion, just like a solid object.
Pressure (in fluids)
The force exerted per unit area by a fluid, acting perpendicularly to any surface in contact with it, and increasing with depth.
Example:
Deep-sea submersibles are built to withstand immense pressure from the surrounding ocean water.
Turbulent Flow
A type of fluid flow characterized by chaotic, irregular motion with eddies and swirls, often occurring at high speeds or around obstacles.
Example:
The swirling, frothy water downstream from a waterfall is a classic example of turbulent flow.
Viscosity
A measure of a fluid's resistance to flow, arising from the internal friction and cohesion between its particles.
Example:
Molten lava flows slowly down a volcano due to its extremely high viscosity.
Volume of Displaced Fluid
The specific spatial extent of the fluid that is pushed aside by an object, which is a crucial factor in calculating the buoyant force.
Example:
To determine how much buoyant force acts on a partially submerged iceberg, you must calculate the volume of displaced fluid, not the iceberg's total volume.