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Pressure (WJEC GCSE Physics)

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Leander

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Leander

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Pressure

  • Pressure is exerted when a force acts over an area
  • Therefore, pressure can be calculated using:

pressure space equals fraction numerator space force over denominator area end fraction

p space equals fraction numerator space F over denominator A end fraction

  • Where:
    • p = pressure measured in pascals (Pa)
      • 1 pascal is equivalent to 1 newton per meter squared
      • 1 Pa = 1 N / m2
    • F = force measured in newtons (N)
    • A = area measured in metres squared (m2)

  • The area should always be the cross-sectional area of the object
  • So that the force is at a right angle to the surface it is acting upon

  • Higher Tier students will need to be able to rearrange the pressure equation

Pressure, Force, Area Equation Triangle

Pressure triangle (2), IGCSE & GCSE Physics revision notes

Cover up the variable you need to calculate, and the triangle shows you how the equation is arranged

  • Pressure can be exerted by a solid on another solid
    • For example the pressure exerted by a person standing on the ground
  • Pressure can be exerted by a gas on a surface
    • For example when gas particles collide with the surfaces of a container

Gas Particles Colliding with the Walls of a Container

Random motion of gas particles, IGCSE & GCSE Chemistry revision notes

Gas particles collide with the surfaces of a container producing a force that acts over an area

Worked example

The particles in a gas exert a force of 0.3 N on a surface of 0.025 m2.

Calculate the pressure exerted on the surface by the gas.

 

Answer:

Step 1: List the known quantities

  • Force, F = 0.3 N
  • Area, A = 0.025 m2

Step 2: Write out the equation for pressure

p space equals fraction numerator space F over denominator A end fraction

Step 3: Substitute in the known values to calculate

p space equals fraction numerator space 0.3 over denominator 0.025 end fraction

p space equals space 12 space Pa

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    Leander

    Author: Leander

    Expertise: Physics

    Leander graduated with First-class honours in Science and Education from Sheffield Hallam University. She won the prestigious Lord Robert Winston Solomon Lipson Prize in recognition of her dedication to science and teaching excellence. After teaching and tutoring both science and maths students, Leander now brings this passion for helping young people reach their potential to her work at SME.