Glossary
Density
A fundamental property of matter defined as the ratio of an object's mass to its volume, indicating how much mass is packed into a given space.
Example:
A small lead fishing weight sinks in water because its high density means it has more mass packed into its small volume than the water it displaces.
Fluids
Substances that can flow and do not have a fixed shape, encompassing both liquids and gases.
Example:
When you pour water into a glass, the water is a fluid that takes the shape of the container.
Gases
A state of matter with very weak intermolecular forces, allowing particles to move randomly and independently, taking both the shape and volume of their container.
Example:
The gas inside a balloon expands to fill the entire balloon, regardless of its initial shape.
Ideal fluids
A theoretical simplification of fluids used in physics to make calculations easier, characterized by being incompressible and having zero viscosity.
Example:
When analyzing the flow of water through a wide pipe at low speeds, physicists might approximate it as an ideal fluid to simplify the calculations.
Incompressible
A property of an ideal fluid (or real fluid under certain conditions) where its density remains constant regardless of changes in pressure.
Example:
Water is often considered incompressible in everyday scenarios, which is why a hydraulic brake system works by transmitting force without significant volume change.
Liquids
A state of matter where weaker intermolecular forces allow particles to move freely, taking the shape of their container while maintaining a fixed volume.
Example:
The liquid mercury in a thermometer expands and contracts, but its volume remains constant unless heated or cooled significantly.
Solids
A state of matter where strong intermolecular forces keep particles locked in fixed positions, giving them a fixed shape and volume.
Example:
An ice cube maintains its rigid shape and volume even when moved to a different container because it's a solid.
Zero Viscosity
A property of an ideal fluid indicating that it flows without any internal friction or resistance between its layers.
Example:
Unlike thick honey, which has high viscosity, an ideal fluid would flow perfectly smoothly through a narrow tube with no energy loss due to internal friction.