5.5.1 Pressure

Understanding Pressure

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In a gas, particles are constantly moving randomly in all directions. As these particles collide with the walls of their container, they exert forces on the surfaces. The cumulative effect of these countless collisions is what we experience as pressure.

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Example: The pressure inside a car tyre supports the weight of the vehicle. If the area of the tyre in contact with the road is reduced (e.g., by under-inflation), the pressure must increase to support the same weight, potentially leading to tyre damage.

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Formula for Pressure The pressure exerted on a surface is calculated using the formula:

\text{pressure}, p = \frac{\text{force}}{\text{area}} = \frac{F}{A}

Pressure ( $p$ ): Measured in pascals (Pa), where 1 Pa is equivalent to 1 newton per square meter $(1Pa =1N/m^2)$ .
Force ( $F$ ): Measured in newtons (N), representing the push or pull exerted by the gas particles.
Area ( $A$ ): Measured in square meters $(m^2)$ , representing the surface area over which the force is distributed.

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Important Note Pressure always produces a net force that acts perpendicularly (at right angles) to any surface. This is why, for example, a balloon expands equally in all directions when it is inflated.

Example Calculations

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Example 1: Calculating Pressure on a surface Problem: A force of 200 N is applied evenly across a surface with an area of 0.5 $m^2$ . What is the pressure exerted on the surface?

Solution:

Identify the given values:

Force (F) = 200 $N$
Area (A) = 0.5 $m^2$

Use the pressure formula: Answer: The pressure exerted on the surface is 400 pascals (Pa).

Pressure Simplified Revision Notes for GCSE AQA Physics

5.5.1 Pressure

Understanding Pressure

Example Calculations

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