# 18 Lecture

## Physics of Fluids

The physics of fluids is used in a variety of industries, including engineering, aerospace, and environmental sciences.

## Important Mcq's Midterm & Finalterm Prepration Past papers included

What is the relationship between pressure and velocity in a fluid, according to Bernoulli's principle?

A. Pressure and velocity are directly proportional

B. Pressure and velocity are inversely proportional

C. Pressure and velocity are not related

D. None of the above

Answer: B. Pressure and velocity are inversely proportional

What is the unit of viscosity?

A. kg/m³

B. m/s²

C. Pa·s

D. J/kg

What is the term for the force per unit area acting on a surface in contact with a fluid?

A. Buoyancy

B. Pressure

C. Surface tension

D. Viscosity

Which type of fluid flow occurs when the fluid moves in a straight line at a constant velocity?

A. Laminar flow

B. Turbulent flow

C. Transitional flow

D. Viscous flow

What is the term for the ratio of a fluid's density to its viscosity?

A. Mach number

B. Reynolds number

C. Weber number

D. Froude number

What is the term for the point in a fluid flow where the velocity is at its maximum and the pressure is at its minimum?

A. Stagnation point

B. Separation point

C. Vortex point

D. Turbulent point

Which principle states that the total pressure in a fluid flow system is constant?

A. Pascal's principle

B. Archimedes' principle

C. Bernoulli's principle

D. Hooke's principle

What is the term for the upward force on an object submerged in a fluid?

A. Pressure

B. Buoyancy

C. Drag

D. Lift

What is the term for the resistance of a fluid to flow?

A. Viscosity

B. Surface tension

C. Compressibility

D. Reynolds number

Which type of fluid flow occurs when the fluid moves in a chaotic and unpredictable manner?

A. Laminar flow

B. Turbulent flow

C. Transitional flow

D. Viscous flow

## Subjective Short Notes Midterm & Finalterm Prepration Past papers included

What is the Navier-Stokes equation, and what does it describe?

Answer: The Navier-Stokes equation is a set of equations that describe the conservation of momentum and mass in a fluid. It describes the motion of fluids, including liquids and gases, under various conditions.

What is turbulence, and how does it occur in fluids?

Answer: Turbulence is a chaotic and unpredictable flow behavior that occurs when fluids are subjected to high velocities or shear forces. It is characterized by eddies and vortices that cause fluctuations in velocity and pressure.

What is viscosity, and how is it affected by temperature and pressure?

Answer: Viscosity is the resistance of a fluid to flow. It is dependent on the internal friction between the molecules of a fluid and can be affected by temperature, pressure, and the presence of other substances in the fluid.

What is surface tension, and how does it influence the behavior of liquids?

Answer: Surface tension is the tendency of the surface of a liquid to minimize its surface area, which causes liquids to form spherical droplets or to wet surfaces. This property is important in the behavior of liquids in capillary tubes, where the surface tension can cause the liquid to rise or fall depending on the angle of the tube.

What is Bernoulli's principle, and how is it used in engineering?

Answer: Bernoulli's principle states that as the velocity of a fluid increases, the pressure of the fluid decreases. This principle is used in a variety of applications, including the design of airplane wings and the operation of carburetors in engines.

How does the behavior of gases differ from that of liquids?

Answer: Gases are much more compressible than liquids and have no definite volume or shape. The behavior of gases is described by the ideal gas law, which relates the pressure, temperature, and volume of a gas.

What is compressibility, and how does it relate to the behavior of gases?

Answer: Compressibility is the ability of a substance to be compressed or expanded under different conditions. Gases are highly compressible, which makes them useful in a variety of applications, such as in the operation of internal combustion engines.

What is the role of fluid dynamics in medicine?

Answer: Fluid dynamics is used in medicine to study blood flow and respiratory systems. Understanding the behavior of fluids in the human body can help diagnose and treat a variety of medical conditions.

How does the study of fluid mechanics contribute to the design of ships and boats?

Answer: The study of fluid mechanics is important in the design of ships and boats because it allows engineers to understand the behavior of water and waves under different conditions. This knowledge is used to design vessels that are safe and efficient in a variety of weather and water conditions.

What is the practical application of the physics of fluids in weather forecasting?

Answer: The physics of fluids is used in weather forecasting to study the behavior of atmospheric gases and water vapor. This information is used to predict weather patterns, including the movement of storms and the development of severe weather conditions.

### Physics of Fluids

The study of fluids, including liquids and gases, falls under the umbrella of the physics of fluids. This field of study involves understanding the behavior and properties of fluids under various conditions and how they interact with different materials and objects. The physics of fluids is used in a variety of industries, including engineering, aerospace, and environmental sciences. One of the key properties of fluids is their ability to flow, which is in contrast to the rigid structure of solids. This flow behavior is due to the lack of a definite shape or volume, which allows fluids to conform to the shape of their container. The motion of fluids is governed by a set of equations known as the Navier-Stokes equations, which describe the conservation of momentum and mass in a fluid.

### Turbulence

One of the most interesting phenomena in the physics of fluids is turbulence. Turbulence is a chaotic and unpredictable flow behavior that occurs when fluids are subjected to high velocities or shear forces. Turbulence is characterized by eddies and vortices that cause fluctuations in velocity and pressure, which can be seen in the swirling motion of water in a stream or the chaotic flow of air around an airplane wing. Another important property of fluids is viscosity, which is the resistance of a fluid to flow. Viscosity is dependent on the internal friction between the molecules of a fluid and can be affected by temperature, pressure, and the presence of other substances in the fluid. High viscosity fluids, such as honey or molasses, flow slowly, while low viscosity fluids, such as water or gasoline, flow more easily. The behavior of fluids is also influenced by external forces, such as gravity and surface tension. Surface tension is the tendency of the surface of a liquid to minimize its surface area, which causes liquids to form spherical droplets or to wet surfaces. This property is important in the behavior of liquids in capillary tubes, where the surface tension can cause the liquid to rise or fall depending on the angle of the tube. The study of fluids also encompasses the behavior of fluids in motion. One of the key principles in this area is Bernoulli's principle, which states that as the velocity of a fluid increases, the pressure of the fluid decreases. This principle is used in a variety of applications, including the design of airplane wings and the operation of carburetors in engines. The study of fluid mechanics also involves understanding the behavior of fluids in different states, such as gases and liquids. One of the key properties of gases is their compressibility, which allows them to be easily compressed or expanded under different conditions. The behavior of gases is described by the ideal gas law, which relates the pressure, temperature, and volume of a gas. Liquids, on the other hand, are much less compressible than gases and have a definite volume but no definite shape. The behavior of liquids is influenced by their interaction with solid surfaces, such as in the case of capillary action, or the rise of liquids in narrow tubes. The physics of fluids has a wide range of practical applications, from the design of airplanes and ships to the study of ocean currents and weather patterns. Understanding the behavior of fluids is also important in fields such as medicine, where fluid dynamics are used to study blood flow and respiratory systems. In conclusion, the physics of fluids is a fascinating field that encompasses the behavior and properties of liquids and gases. The study of fluids involves understanding the complex interactions between different properties, such as viscosity, surface tension, and turbulence, and how they influence the behavior of fluids in different states and under different conditions. The practical applications of the physics of fluids are vast and varied, making it an important field of study in both academic and industrial settings.