Liquid pressure refers to the force per unit area exerted by a liquid on its surroundings, typically a container or any object immersed in it. It is a measure of how much force the liquid exerts on a given area.
The mathematical form of liquid pressure is determined by the fundamental equation:
P=F/A
Where:
- P is the liquid pressure,
- F is the force exerted by the liquid,
- A is the area over which the force is applied.
This equation indicates that pressure is directly proportional to force and inversely proportional to the area over which the force is distributed.
Properties of Liquid Pressure
| No. | Property | Definition | Formula | Example |
|---|---|---|---|---|
| 1 | Depth-dependent | Liquid pressure increases with depth in a fluid | P=ρ⋅g⋅h | If ρ=1000 kg/m³, g=9.8 m/s², h=5m, P=49,000 Pa or 4949 kPa |
| 2 | Direction | Liquid pressure is transmitted equally in all directions | No specific formula; pressure is omnidirectional | Hydrostatic Paradox: pressure is the same regardless of the shape of the container |
| 3 | Hydrostatic Paradox | Pressure at a given depth is independent of container shape | No specific formula; equal pressure at the same depth regardless of container shape | U-shaped tube with water, pressure is equal on both sides |
| 4 | Density-dependent | Liquid pressure is directly proportional to its density | P=ρ⋅g⋅h | Using mercury (ρ≈13,600 kg/m³) at the same depth as the water example |
| 5 | Pressure in a confined liquid | Pressure applied to a confined fluid is transmitted undiminished in all directions | Pascal’s Law – Pexternal=Pinternal | Squeezing a sealed container increases pressure uniformly |
| 6 | Buoyancy | Objects submerged in a fluid experience an upward force equal to the weight of the fluid displaced | Archimedes’ Principle – Fbuoyancy=ρfluid⋅g⋅Vdisplaced | 1 kg block of wood submerged in water displacing 1 liter (1 kg) of water, buoyant force 9.8 N |
Real Life Examples
| Real-Life Examples | Description |
|---|---|
| Hydraulic Systems | In car brake systems, liquid pressure is employed to transmit force. Pressing the brake pedal increases the liquid pressure in the brake fluid, activating the brakes and facilitating the deceleration of the vehicle. |
| Blood Circulation | In the human body, blood exerts pressure on the walls of blood vessels. This blood pressure is crucial for maintaining blood circulation, ensuring the delivery of oxygen and nutrients to various parts of the body. |
| Water Towers | Water towers utilize liquid pressure to supply water to homes and businesses. The elevated tank, through gravitational potential energy, generates pressure as water descends, ensuring a consistent and reliable water supply through the pipes. |
| Swimming Pool Depth | The pressure at the bottom of a swimming pool increases with depth. As one descends deeper into the pool, the liquid pressure rises due to the cumulative weight of the water above, creating varying pressure levels at different depths. |
| Syringe Operation | When the plunger of a syringe is pushed, the applied force decreases the volume inside, thereby increasing the liquid pressure. This pressure disparity compels the expulsion of liquid (medicine) through the needle, allowing for controlled administration. |
| Dams and Reservoirs | Dams harness liquid pressure to generate hydroelectric power. Stored water at a higher elevation creates substantial pressure, and this potential energy is converted into electricity as the water flows downward through turbines, illustrating the utilization of liquid pressure in energy generation. |
