Chapter 13 - Forces in Fluids

Pressure and Its Calculation

• Pressure is defined as the result of a force distributed over an area.
• Calculating pressure involves dividing the force by the area (Pressure = force/area).
• The Pascal (Pa) is the SI unit of pressure, equivalent to newtons per square meter (N/m²).

Fluid Characteristics

• Fluids are substances that take the shape of their container, encompassing both liquids and gases.
• Water pressure increases with depth due to the weight of the water above.

Pressure Behavior in Fluids

• At any given depth in a fluid, pressure remains constant and acts equally in all directions.
• Factors influencing static fluid pressure include depth and the type of fluid.

Atmospheric Pressure

• The weight of Earth's atmosphere exerts a pressure of approximately 101 kPa.
• Air pressure rises with increasing atmospheric depth, while it decreases at higher altitudes.

Forces and Balance

• Inside a body, pressure balances the external air pressure, resulting in a net force of zero, indicating balanced forces.

Fundamental Principles

• Pascal's Principle states that any change in pressure at any point in a fluid is transmitted equally in all directions.
• Hydraulic systems utilize pressurized fluids acting on pistons of varying sizes to modify force, where increased area leads to increased output force.

Fluid Dynamics

• According to Bernoulli's Principle, the speed of a fluid increases while its pressure decreases, affecting lift generation.
• Lift is the upward force created by pressure differences.

Buoyancy and Its Principles

• Buoyancy refers to a fluid's ability to exert an upward force on an object placed within it.
• The phenomenon of buoyancy is caused by an apparent loss of weight of objects submerged in fluids.

Buoyant Forces and Conditions

• Buoyant force acts in the opposite direction to gravity and is equal to the weight of the fluid displaced, as per Archimedes' Principle.
• An object's density influences its flotation ability; less dense objects can float better, while denser objects struggle to remain afloat.

Floating and Sinking Criteria

• An object will float when its buoyant force equals its weight, while sinking occurs when the buoyant force is less than the object's weight.
• Objects can remain suspended in a fluid when the buoyant force matches their weight.

Effects of Area and Liquid Density

• The greater the area of an object in a fluid, the higher the buoyant force it experiences.
• Denser liquids provide a greater weight displacement, resulting in increased buoyant force.