Pressure

Fluid Pressure

Both gases and liquids are fluids because their particles can move freely.

Fluid pressure is the result of collisions between particles in a gas or liquid and the surface they are in contact with.

• Increasing surface area decreases the pressure because the same force is spread over a larger area.

Factors Affecting Fluid Pressure

Fluid pressure depends on:

1. Area: Larger surface areas reduce pressure as the force is distributed over more space.
2. Properties of the Fluid:

• Density: Denser fluids exert more pressure because there are more particles in a given space, leading to more collisions.
• Temperature: Higher temperatures increase the speed of particles, raising pressure.

3. Surrounding Atmospheric Pressure: This is the pressure exerted by the air around us. At higher altitudes, atmospheric pressure is lower because there are fewer air particles.

Pressure in Gases vs. Liquids

Liquids: The density is the same throughout a liquid, so pressure increases steadily with depth.

Gases: The density and pressure of gases can change based on temperature, volume, and surrounding atmospheric pressure.

Pressure and Depth

Pressure in a fluid increases with depth. This is because the weight of the particles above adds to the pressure at any given point. The deeper you go in a fluid, the more particles there are pushing down from above.

Atmospheric Pressure

Applications of Pressure

1. Hydraulics: Hydraulics use the principle of pressure in liquids to lift heavy objects. The pressure applied to one part of a hydraulic system is transmitted through the fluid, allowing a small force to create a larger force at another point.

2. Aeroplanes: Aeroplanes rely on differences in air pressure above and below the wings to generate lift. The pressure below the wing is higher, pushing the airplane upward.

3. Diving: Divers experience increasing water pressure as they go deeper. Specialised equipment is used to prevent the body from being crushed by the high pressure at great depths.