Part 2/9:
Pressure, in its simplest form, is the force applied over a unit area. For example, consider a cube of iron placed on a smartphone screen. When the cube is placed flat, the screen bears minimal stress. However, if positioned on its corner, the pressure increases significantly, potentially cracking the screen. This example demonstrates how our ancestors understood pressure intuitively, leading to inventions like sharpened spears and nails long before they could measure it.