Glossary
Bernoulli Equation
A principle in fluid dynamics that relates fluid speed, pressure, and height, stating that an increase in fluid speed occurs simultaneously with a decrease in pressure or potential energy.
Example:
The lift on an airplane wing is explained by the Bernoulli Equation, where faster-moving air above the wing creates lower pressure.
Boyle's Law
A gas law stating that for a fixed amount of gas at constant temperature, the pressure and volume are inversely proportional.
Example:
When you push down on a bicycle pump, the volume of air decreases, and its pressure increases, illustrating Boyle's Law.
Buoyant Force
The upward force exerted by a fluid that opposes the weight of an immersed object, caused by the pressure difference between the top and bottom of the object.
Example:
A hot air balloon rises because the buoyant force from the surrounding cooler air is greater than the balloon's weight.
Closed Systems
Systems that allow energy but not matter (fluid) to cross their boundaries, meaning the fluid mass within remains constant.
Example:
A sealed bottle of soda is a closed system because no liquid or gas can enter or leave.
Density
A measure of mass per unit volume of a substance, indicating how much 'stuff' is packed into a given space.
Example:
A lead sinker sinks in water because its density is greater than that of water.
Fluid Mechanics
The branch of physics that studies the behavior of fluids (liquids, gases, and plasmas) and the forces on them.
Example:
Designing an airplane wing involves principles of fluid mechanics to understand lift and drag.
Fluid Properties
Measurable characteristics of a fluid that describe its physical behavior, such as density, viscosity, and surface tension.
Example:
Understanding the fluid properties of honey, like its high viscosity, explains why it pours slowly.
Fluid System
Any system involving the flow or behavior of a fluid, encompassing both liquids and gases.
Example:
A hydraulic brake line in a car is a fluid system where liquid pressure transmits force.
Fluids
Substances that can flow and do not have a fixed shape, taking the shape of their container. This category includes both liquids and gases.
Example:
Water, air, and oil are all common examples of fluids that can be poured or compressed.
Gases
A state of matter that has neither a definite volume nor a definite shape, expanding to fill its container.
Example:
The air inside a balloon is a gas that expands to fill the entire volume of the balloon.
Internal Structure
The arrangement and interactions of the constituent particles (atoms or molecules) within a fluid or system, which significantly influence its macroscopic properties.
Example:
The strong intermolecular forces in water give it a high internal structure that contributes to its surface tension.
Liquids
A state of matter that has a definite volume but no fixed shape, conforming to the shape of its container.
Example:
When you pour juice into a glass, the liquid takes the exact shape of the glass.
Object
A single physical entity or a distinct 'thing' that can be analyzed, often as part of a larger system.
Example:
In a problem involving a car, the car itself can be considered an object for analyzing its motion.
Open Systems
Systems that allow both matter (fluid) and energy to flow in and out across their boundaries.
Example:
A river flowing into the ocean is an open system because water continuously enters and leaves.
Salt Water
Water containing dissolved salts, which typically has a higher density than pure fresh water.
Example:
A ship floats higher in salt water than in fresh water due to the greater buoyant force exerted by the denser liquid.
Surface Tension
The cohesive forces between liquid molecules at the surface that cause the liquid to behave like an elastic sheet.
Example:
A water strider can walk on water due to the strong surface tension of the water.
System
A group of interacting objects or components whose collective behavior is the focus of study.
Example:
A car's engine, cooling system, and fuel system together form a complex system that enables the car to run.
Viscosity
A measure of a fluid's resistance to flow, indicating its 'thickness' or internal friction.
Example:
Motor oil has a specific viscosity to ensure it lubricates engine parts effectively at different temperatures.