FLUID STATICS & FLUID DYNAMICS

PRERNA FOR IAS

FLUID STATICS & FLUID DYNAMICS

1. Pressure in a Fluid

Pressure in a fluid is the force exerted per unit area by a liquid or gas. In a stationary fluid, pressure increases with depth because the weight of the fluid above increases. The pressure at a depthis given by the formula, whereis density,is gravitational acceleration, andis depth. Total pressure includes atmospheric pressure acting on the fluid surface. Fluid pressure acts equally in all directions and is an important concept in dams, water tanks, submarines, and hydraulic systems. Understanding fluid pressure helps explain many natural and engineering phenomena.

2. Buoyancy (Upthrust)

Buoyancy is the upward force exerted by a fluid on an object immersed in it. This force opposes the object's weight and is responsible for floating and sinking. According to Archimedes’ Principle, the buoyant force equals the weight of the displaced fluid. The formula is, whereis the volume of displaced fluid. If buoyancy exceeds weight, the object floats; otherwise, it sinks. Buoyancy plays a vital role in ships, submarines, balloons, and aquatic life. It explains how massive ships made of steel can float while smaller dense objects may sink.

3. Surface Tension

Surface tension is the property of a liquid surface that makes it behave like a stretched elastic membrane. It arises because molecules at the surface experience unequal attractive forces. Surface tension is defined as force per unit length and is represented by. It enables insects to walk on water and causes water droplets to form spherical shapes. Surface tension is important in capillary action, detergents, biological processes, and industrial applications. Liquids with strong intermolecular forces generally have higher surface tension. Temperature affects surface tension, usually decreasing it as temperature increases.

4. Surface Energy

Surface energy is the energy required to increase the surface area of a liquid. Since molecules at the surface possess excess energy compared to those inside the liquid, work must be done to create additional surface area. Surface energy is directly related to surface tension and is expressed as, whereis surface tension andis surface area. This concept helps explain why soap bubbles, droplets, and liquid films behave in specific ways. Surface energy is important in material science, coatings, adhesives, and biological systems where surface interactions significantly influence behavior and efficiency.

5. Angle of Contact