Pressure

“Pressure is defined as the force applied per unit area in a direction perpendicular to the surface.”

Definition and Formula

Pressure is the amount of force exerted on a surface per unit area of that surface.

  • Pressure (P) = Force (F) / Area (A)

SI unit of pressure is Pascal (Pa), where 1 Pa = 1 N/m².

Factors Affecting Pressure

  • Directly proportional to the force applied.
  • Inversely proportional to the area on which the force is applied.

Smaller area → more pressure (e.g., knife edge), larger area → less pressure (e.g., snowshoes).

Pressure in Fluids

Fluids (liquids and gases) exert pressure in all directions. This is the principle behind hydraulic systems.

Fluid pressure increases with depth.

Thrust

Thrust is the total force acting perpendicular to a surface. It is measured in Newtons (N).

Pressure is the effect of thrust on a unit area.

Atmospheric Pressure

The pressure exerted by the weight of air in the Earth's atmosphere is called atmospheric pressure.

  • Standard atmospheric pressure at sea level is 1.013 × 10⁵ Pa.

Measured using a barometer.

Variation of Pressure with Height

Atmospheric pressure decreases with increase in height from sea level. This is why mountain climbers carry oxygen cylinders.

Previous Year Questions

  • SSC CHSL 2021: What is the SI unit of pressure?
  • Pascal
  • HSSC JE 2018: What happens to atmospheric pressure as altitude increases?
  • It decreases
  • RRB JE 2019: Instrument used to measure atmospheric pressure is?
  • Barometer

Applications of Pressure

  • Hydraulic brakes use pressure in liquids to apply force.
  • Knives have sharp edges to concentrate force and increase pressure.
  • Wide shoes reduce pressure on snow and prevent sinking.
Did you know? Astronauts wear pressurized suits because there's almost no atmospheric pressure in space.

Conclusion

Pressure is a crucial physical quantity in both daily life and industrial applications. Understanding pressure helps us design systems involving fluids, gases, and mechanical equipment effectively.

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