Pressure and pressure differences in fluids — WJEC GCSE Physics
In summary: Pressure and pressure differences in fluids is a key topic in WJEC GCSE Physics. Key exam tip: Always ensure force is in Newtons and area is in square metres when using the pressure equation
Exam Tips for Pressure and pressure differences in fluids
- Always ensure force is in Newtons and area is in square metres when using the pressure equation
- Remember that the pressure in a liquid depends on the vertical depth, not the shape of the container
- Be prepared to explain why atmospheric pressure decreases as altitude increases due to the decreasing density of air
Common Mistakes
- Confusing force and pressure
- Failing to use the correct units for area (m²) when calculating pressure
- Misunderstanding that pressure acts in all directions in a fluid
- Incorrectly identifying the factors that determine floating and sinking
Marking Points
- Pressure = force normal to a surface / area of that surface
- Pressure in a liquid increases with depth and density
- Atmospheric pressure decreases with height above the surface
- Upwards force on a partially submerged object is caused by pressure differences
- Pressure due to a column of liquid = height of column × density of liquid × gravitational field strength (p = hρg)
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