Pressure in Liquids (Edexcel IGCSE Physics)

• A fluid is either a liquid or a gas
• When an object is immersed in a fluid, the fluid will exert pressure, squeezing the object
  • This pressure is exerted evenly across the whole surface of the fluid and in all directions
  • The pressure exerted on objects in fluids creates forces against surfaces
  • These forces act at 90 degrees (at right angles) to the surface

The pressure of a fluid on an object creates a force normal (at right angles) to the surface

• The pressure due to a column of liquid can be calculated using the equation

p = h × ρ × g

• Where:
  • p = pressure in pascals (Pa)
  • h = height of the column in metres (m)
  • ρ = density of the liquid in kilograms per metre cubed (kg/m³)
  • g = gravitational field strength on Earth in newtons per kilogram (N/kg)

• The force from the pressure is exerted evenly across the whole surface of an object in a liquid, and in all directions

The force from the pressure of objects in a liquid is exerted evenly across its whole surface

• The pressure is more accurately the difference in pressure at different depths h in a liquid, since the pressure changes with the depth