Pressure Calculation and Applications

Pressure Calculation

• Pressure is defined as force per unit area. It indicates how a force affects a surface.

Pressure and Shoe Types

• Different shoe types exert different pressures due to variations in their surface area.
• Flat shoes distribute force over a broader area, decreasing pressure. This is useful for walking on soft surfaces like snow, as snowshoes have a large area, significantly reducing pressure on the ground.
• High-heeled shoes concentrate force on a smaller area, leading to increased pressure. This makes stepping on someone's foot in heels more painful than with flats. Similarly, stepping on small objects barefoot increases pressure, intensifying pain.

Pressure in Fluids

• Liquids and gases are fluids.

• Fluid pressure applies a force perpendicular (normal) to a surface.

• The pressure within a fluid can be calculated using the formula:

  • Pressure (p) = Force (F) normal to a surface / Area (A) of the surface
  • p = F / A

• Units for calculations:

  • Pressure (p) is measured in pascals (Pa)
  • Force (F) is measured in newtons (N)
  • Area (A) is measured in meters squared (m²)

• Pressure in a liquid increases with depth.

• Pressure in a liquid is due to the weight of the water column above.

• Pressure in a liquid acts in all directions.

• Pressure at the bottom of a body of water is greater than at the top.

• Dam walls are wedge-shaped to withstand the increased pressure at the bottom.

• Pressure is essential for life, enabling blood circulation and respiration.

• Every living thing balances with surrounding air or water pressure.

Example Calculation

• A fluid (example given) with 50N force on an area of 2m² has a pressure of 25 Pa (25 pascals).

Further Calculation Example

• A fluid with a 150 N force on an area of 1.2 m² exerts a pressure of 125 Pa.

Pressure in Different Depths

• The pressure exerted by a liquid is calculated using : p = ρgh, where:
  • ρ (rho) = density of the liquid (kg/m³)
  • g = gravitational field strength (N/kg)
  • h = depth (m)
• An object submerged in a liquid experiences a greater pressure on its bottom surface than its top surface. This generates a resultant force upwards.
• This force is called upthrust.
• If upthrust is less than an object's weight, the object sinks.
• If upthrust is greater than an object's weight, the object floats.

Atmospheric Pressure

• The atmosphere is the layer of gases surrounding Earth; key gases include nitrogen, oxygen, and carbon dioxide.
• Atmospheric pressure is caused by air molecules colliding with surfaces.
• Atmospheric pressure at sea level is approximately 101,000 Pa (101 kPa).
• Atmospheric pressure decreases with increasing altitude.
• At the cruising altitude of a passenger plane, atmospheric pressure is about 27,000 Pa (27 kPa).
• Aircraft flying at high altitudes must be pressurized to maintain sufficient oxygen for occupants, as lower pressure limits oxygen intake.

This quiz explores the concept of pressure, defined as force per unit area, and its application in different contexts such as shoe types and fluids. Learn how different shoes impact pressure distribution and how to calculate fluid pressure using the essential formula. Test your understanding of these principles and their practical implications.