Pressure can be defined as the amount of force applied perpendicular to the surface of an object per unit area over which the force is distributed. It is a measure of the intensity or magnitude of the force exerted on a surface.
The key difference between pressure and force per unit area lies in their definitions and units of measurement. Force per unit area, also known as stress, is the measure of the force applied to a given area, while pressure specifically refers to the force applied perpendicular to a surface.
In simple terms, force per unit area (stress) is a more general term that can refer to force applied in any direction, not necessarily perpendicular to the surface. Pressure, on the other hand, is a specific type of stress that is always applied perpendicular to the surface.
Mathematically, pressure (P) is calculated by dividing the magnitude of the force (F) applied perpendicular to the surface by the area (A) over which the force is distributed:
Pressure (P) = Force (F) / Area (A)
The unit of pressure in the International System of Units (SI) is the pascal (Pa), which is equal to one newton per square meter (N/m²). Force per unit area (stress) can be measured in various units depending on the context, such as pascals, pounds per square inch (psi), or dynes per square centimeter (dyn/cm²).
In summary, pressure specifically refers to the force applied perpendicular to a surface per unit area, while force per unit area (stress) is a broader term encompassing force applied in any direction per unit area.