Pressure Exerted By Liquids And Gases

key notes:

Pressure in Liquids:

  1. Pressure is the force applied on a surface per unit area. It is measured in Pascals (Pa), where 1 Pascal is equal to 1 Newton per square meter (1 Pa = 1 N/m²).

2. Liquids exert pressure in all directions. This is because the weight of liquid molecules above a certain point causes pressure.

  1. Pressure in a liquid increases with depth. The deeper you go in a liquid, the higher the pressure due to the increased weight of the liquid above.
  2. Pascal’s Principle: Pascal’s principle states that a change in pressure applied to an enclosed fluid is transmitted undiminished to all portions of the fluid and to the walls of its container.

Hydraulic Systems:

5. Hydraulic systems use the principle of transmitting pressure through liquids to amplify force. It’s commonly used in brakes, car lifts, and heavy machinery.

  1. In a hydraulic system, a small force applied to a small piston generates a larger force on a larger piston due to the transmission of pressure through the liquid.

Pressure in Gases:

7. Gases also exert pressure, but unlike liquids, this pressure is due to the constant motion of gas molecules.

  1. Boyle’s Law: Boyle’s law states that at constant temperature, the pressure of a gas is inversely proportional to its volume. P1V1 = P2V2, where P1 and V1 are initial pressure and volume, and P2 and V2 are final pressure and volume.
  2. Charles’s Law: Charles’s law states that at constant pressure, the volume of a gas is directly proportional to its absolute temperature (in Kelvin). V1/T1 = V2/T2, where V1 and T1 are initial volume and temperature, and V2 and T2 are final volume and temperature.

Applications:

10. Understanding pressure in liquids and gases is crucial for various applications like scuba diving, weather forecasting, and designing hydraulic machines.

  1. Atmospheric pressure decreases with increasing altitude, which is why it’s harder to breathe at high altitudes.

Measuring Pressure:

12. Pressure is measured using instruments like barometers for atmospheric pressure and manometers for pressure in closed systems.

  1. Common units for pressure include atmospheres (atm), millimeters of mercury (mmHg), and pounds per square inch (psi).

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