Phy6 Fluid mechanics Flashcards
What is fluid mechanics?
A branch of physics that deals with the study of fluids at rest and in motion
It has applications in engineering, meteorology, and biology.
Define a fluid.
A substance that can flow and take the shape of its container
Fluids include both liquids and gases.
What are the properties of solids?
- Definite shape
- Fixed volume
- Tightly packed particles
- Incompressible
- High density
Examples include metals, wood, and rocks.
What are the properties of liquids?
- No fixed shape
- Definite volume
- Loosely bonded particles
- Slightly compressible
- Lower density compared to solids
Examples include water, oil, and milk.
What are the properties of gases?
- No fixed shape
- No definite volume
- Free-moving particles
- Easily compressible
- Lowest density among states of matter
Examples include air, oxygen, and carbon dioxide.
What is pressure in fluids?
Force exerted per unit area on an object immersed in or in contact with the fluid
Fluid pressure applies in all directions.
Define hydrostatic pressure.
Pressure exerted by a fluid at rest due to the weight of the fluid above it
Hydrostatic pressure increases with depth.
What is vapor pressure?
The pressure exerted by the vapor of a substance
It is relevant in various chemical and physical processes.
What is the SI unit of pressure?
Pascal (Pa)
Defined as one newton per square meter.
What is an atmosphere (atm) in terms of pressure?
A unit of pressure equal to 101,325 pascals
Commonly used in weather reports.
What is the relationship between gas pressure and the number of gas molecules?
An increase in the number of gas molecules increases the pressure
A decrease in the number of molecules decreases the pressure.
What effect does temperature have on gas pressure?
An increase in temperature increases kinetic energy and pressure
A decrease in temperature results in decreased pressure.
What does the ideal gas equation represent?
The behavior of gases under various conditions
Written as PV = nRT.
Define density.
Mass of a substance per unit volume
Commonly expressed in g/cm³ or kg/m³.
What is relative density?
Measure of the density of a substance compared to a reference substance
Often compared to the density of water.
What is Pascal’s principle?
A change in pressure at any point in an enclosed incompressible fluid is transmitted equally in all directions
This principle is fundamental in hydraulic systems.
What applications utilize Pascal’s principle?
- Hydraulic brakes
- Hydraulic lifts
- Hydraulic presses
These applications demonstrate the force multiplication effect.
What is atmospheric pressure?
Pressure within the Earth’s atmosphere due to the weight of air molecules
Standard atmospheric pressure is approximately 1 atm.
What is gauge pressure?
Pressure referenced against ambient air pressure
Equal to absolute pressure minus atmospheric pressure.
What is the formula for hydrostatic pressure?
P = ρgh
Where P is hydrostatic pressure, ρ is fluid density, g is acceleration due to gravity, and h is depth.
What is the definition of bulk density?
Mass per unit volume of a bulk material
Commonly used for powders or granules.
What is the importance of measuring blood pressure?
Crucial for diagnosing and managing health conditions like hypertension
Regular measurements can help detect high blood pressure early.
What is a barometer used for?
Measures atmospheric pressure
The mercury barometer balances a column of mercury against atmospheric pressure.
What principle do hydraulic lifts use to lift heavy objects?
Pascal’s principle
By applying a small force to a small piston, a larger force can be generated on a larger piston.
What are hydraulic presses used for?
Bending, shaping, and compressing materials
Hydraulic presses use Pascal’s principle to generate a large force.
Name three applications of Pascal’s principle.
- Artesian wells
- Water towers
- Dams
What does Archimedes’ principle state?
An object submerged in a fluid experiences an upward buoyant force equal to the weight of the fluid displaced.
What is the formula for buoyant force according to Archimedes’ principle?
Fb = ρf Vd.f g
What determines whether an object will float or sink in a fluid?
The weight of the fluid displaced by the object compared to the weight of the object.
How does Archimedes’ principle apply to ship design?
It helps determine the buoyancy and stability of ships.
What is the purpose of a hydrometer?
To measure the relative density or specific gravity of liquids.
How do hot air balloons utilize Archimedes’ principle?
The heated air inside is less dense than the surrounding air, causing the balloon to float.
True or False: Archimedes’ principle considers surface tension effects.
False
What is fluid flow?
The movement of a fluid through a system or medium caused by differences in pressure.
What are the two main types of fluid flow?
- Steady (laminar) flow
- Turbulent flow
Define viscous flow.
Flow influenced by internal friction or viscosity.
What characterizes compressible flow?
Changes in fluid density due to variations in pressure and temperature.
What does the equation of continuity express?
Conservation of mass for an incompressible fluid flowing in a tube.
What is the continuity equation formula?
Av = constant ⇒ A1v1 = A2v2
What does Bernoulli’s equation relate to?
Energy conservation in an ideal fluid in motion.
What is a characteristic of high-pressure systems?
Pressures far greater than 1 atmosphere (usually above 50 atm).
List two applications of high pressure.
- High pressure cookers
- Gas cylinders
What is pascalization?
A process that diminishes microorganism activity by applying high pressures.
What is a high-pressure compressor?
A mechanical device that increases the pressure of a gas by reducing its volume.
What do safety accessories in high-pressure equipment include?
- Safety valves
- Bursting discs
- Limiting devices
Name a common cause of pressure system risks.
Damaged equipment or system design
What safety measures are important for high-pressure systems?
Depends on the nature of the high pressure system.
