Describe how pressure varies with force and area in the context of everyday examples

1.8 Pressure

What is Pressure?

Pressure is the force applied per unit area. It tells us how hard a force is spread over a surface.
Mathematically: $P = \dfrac{F}{A}$
Where $P$ = pressure, $F$ = force, $A$ = area.

How Force and Area Affect Pressure

1. Increasing Force: If you keep the area constant and increase the force, pressure rises proportionally.
   Example: pressing harder on a door handle.
2. Increasing Area: If you keep the force constant and increase the area, pressure decreases.
   Example: walking on a wide shoe sole spreads the weight over a larger area, reducing pressure on the ground.
3. Both Change: Pressure can change in either direction depending on how force and area change together.

Everyday Analogies & Examples

• 🍕 Pizza Slice vs Whole Pizza: A single slice (small area) feels heavier than the whole pizza (larger area) even if the total weight is the same.
• 🚶‍♂️ Walking vs Running: Running applies a larger force in a shorter time but the foot area remains similar, so pressure spikes during each footfall.
• 🚗 Tire Pressure: A car tire has a large contact area with the road; higher pressure means the tire can support more weight without deforming.
• 🏊‍♀️ Swimming: The human body has a large surface area relative to its weight, so the pressure on the water surface is low, allowing buoyancy to keep us afloat.
• 🪑 Chair Support: A chair with a wide base spreads your weight over a larger area, reducing pressure on the floor and preventing dents.