Pressure

Definition

Pressure is defined as the force exerted per unit area on a surface, and it plays a vital role in understanding the behavior of fluids and gases. This concept helps explain various phenomena, such as how fluids exert force in different directions and how gases can expand or compress based on their surroundings. Pressure influences many physical properties, including density and buoyancy, which are crucial when analyzing fluid dynamics and gas behavior.

5 Must Know Facts For Your Next Test

1. Pressure is measured in units such as pascals (Pa), atmospheres (atm), or pounds per square inch (psi), with 1 atm being equivalent to 101,325 Pa.
2. In fluids, pressure acts equally in all directions, which means it can support objects submerged within the fluid without preferential direction.
3. An increase in temperature of a gas at constant volume will result in an increase in pressure, demonstrating the relationship between temperature and pressure described by Gay-Lussac's Law.
4. Pressure decreases with altitude in the atmosphere because there is less air above a given point to exert force, leading to lower atmospheric pressure at higher elevations.
5. Bernoulli's Principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure, illustrating how pressure changes can affect fluid flow.

Review Questions

• How does atmospheric pressure vary with altitude, and what implications does this have for flight?
  • Atmospheric pressure decreases with increasing altitude because there is less air above exerting downward force. This reduction in pressure affects aircraft performance, particularly during takeoff and landing phases. As altitude increases, engines may produce less thrust due to lower air density, and pilots must adjust their flight controls accordingly to maintain lift.
• Explain how Pascal's Principle relates to hydraulic systems and their applications.
  • Pascal's Principle states that when pressure is applied to an enclosed fluid, it is transmitted undiminished throughout the fluid. This principle underlies the operation of hydraulic systems, such as hydraulic brakes or lifts. When force is applied at one point in a hydraulic system, it creates equal pressure throughout the fluid, allowing for a greater force to be exerted at another point, enabling efficient mechanical advantage.
• Evaluate the significance of Bernoulli's Principle in aviation and how it contributes to the generation of lift.
  • Bernoulli's Principle is significant in aviation as it explains how differences in airspeed create differences in pressure around an aircraft's wings. According to this principle, as air travels faster over the curved top surface of a wing compared to the slower air beneath it, lower pressure is created above the wing. This pressure difference generates lift, allowing the aircraft to rise and maintain flight. Understanding this concept is essential for designing efficient wings and optimizing flight performance.

Related terms

Atmospheric Pressure: The pressure exerted by the weight of the atmosphere above a given point, typically measured in units such as pascals (Pa) or inches of mercury (inHg).

Hydrostatic Pressure: The pressure exerted by a fluid at rest due to the weight of the fluid above it, commonly observed in liquids and measured using the formula $$P = ho g h$$.

Pascal's Principle: A principle stating that when pressure is applied to an enclosed fluid, it is transmitted undiminished throughout the fluid in all directions.