Properties of fluid- 1 Video Lecture | Crash Course: Mechanical Engineering (ME)

Ans. Fluids have several properties that distinguish them from solids, including: - Viscosity: This property refers to a fluid's resistance to flow. It determines how easily a fluid can be poured or moved. Liquids like water have low viscosity, while substances like honey have high viscosity. - Density: Density is the measure of how much mass is contained in a given volume of fluid. It determines whether a fluid will float or sink in another fluid. For example, oil floats on water because it has a lower density. - Pressure: Pressure is the force exerted per unit area by a fluid. It is responsible for various phenomena, such as buoyancy and fluid flow. Pressure increases with depth in a fluid due to the weight of the fluid above. - Compressibility: Fluids are generally considered to be incompressible, meaning their volume does not change significantly under pressure. However, gases are compressible fluids as their molecules can be compressed closer together. - Surface tension: Surface tension is the property that enables a liquid to resist an external force. It is responsible for phenomena like capillary action and the formation of droplets.

Ans. Viscosity plays a crucial role in determining how a fluid flows. It affects the ease with which a fluid can be poured or moved. Liquids with low viscosity, such as water, flow more easily than fluids with high viscosity, such as honey or molasses. The viscosity of a fluid depends on its internal friction and the resistance between its layers. When a fluid flows, its layers slide past each other, and the resistance encountered determines the viscosity. In terms of fluid flow, viscosity influences the velocity profile and pressure drop within a fluid. Fluids with higher viscosity experience greater resistance to flow, resulting in slower flow rates and higher pressure drops. Conversely, fluids with lower viscosity flow more easily, leading to higher flow rates and lower pressure drops. Understanding the viscosity of a fluid is essential in various engineering applications, such as designing pipelines, hydraulic systems, and lubrication systems.

Ans. Density is a fundamental property that significantly influences the behavior of fluids. It determines whether a fluid will float or sink in another fluid and affects various phenomena like buoyancy and fluid flow. If the density of a fluid is lower than that of the fluid it is immersed in, it will float. For example, oil floats on water because oil has a lower density than water. On the other hand, if the density of a fluid is higher than that of the fluid it is immersed in, it will sink. An example of this is a stone sinking in water. Density also affects fluid flow. When a fluid flows through a pipe or channel, the density of the fluid influences its velocity and pressure. In general, denser fluids require more pressure to achieve the same flow rate as less dense fluids. Understanding the density of a fluid is crucial in designing fluid systems, such as pumps and pipelines, where flow rates and pressures need to be accurately controlled.

Ans. Pressure in a fluid increases with depth. This phenomenon is known as hydrostatic pressure and is caused by the weight of the fluid above. Consider a column of fluid, such as water, in a container. The pressure at the top of the column is lower because there is less fluid above it exerting downward force. As we move down the column, the weight of the fluid above increases, resulting in an increase in pressure. The relationship between pressure and depth in a fluid is given by Pascal's law, which states that the pressure change in a fluid is directly proportional to the depth and density of the fluid. Mathematically, this relationship can be expressed as: Pressure = Density x Gravity x Height Where density is the density of the fluid, gravity is the acceleration due to gravity, and height is the depth at which the pressure is measured. The understanding of how pressure changes with depth is essential in various applications, including calculating fluid pressures in tanks, dams, and underwater systems.

Ans. Surface tension is the property of a liquid that allows it to resist an external force. It is caused by the cohesive forces between the liquid molecules at the surface. At the surface of a liquid, the molecules experience a net inward force due to the cohesive forces with neighboring molecules. This force creates a "skin" or "film" on the liquid's surface, giving it a higher energy state compared to the molecules within the liquid. As a result, the liquid tends to minimize its surface area, forming droplets or adopting a shape with the least surface area. Surface tension has several effects on fluid behavior. It is responsible for capillary action, where liquids rise or fall in narrow tubes due to the balance between adhesive and cohesive forces. Surface tension also enables insects to walk on water and causes liquid droplets to form spherical shapes. In terms of fluid flow, surface tension influences the behavior of liquid films and droplets. It affects the formation and stability of foams and emulsions, as well as the coalescence or breakup of droplets. Understanding surface tension is vital in various industries, including chemistry, biology, and materials science, as it governs the behavior and properties of liquids in different applications.