Pressure is calculated as the force applied perpendicularly to a surface divided by the area over which that force is distributed. This fundamental relationship is expressed by the formula:
p = F/A
Where:
- p = Pressure
- F = Force (measured in Newtons (N) in the SI system)
- A = Area (measured in square meters (m²) in the SI system)
Understanding the Formula
The formula p = F/A tells us that pressure is directly proportional to the force applied. If you increase the force while keeping the area constant, the pressure will increase proportionally. Conversely, pressure is inversely proportional to the area. If you increase the area over which the force is applied while keeping the force constant, the pressure will decrease.
Units of Pressure
The SI unit of pressure is the Pascal (Pa), which is defined as one Newton per square meter (N/m²). Other common units of pressure include:
- Pounds per square inch (psi): Commonly used in the United States.
- Atmosphere (atm): Approximately equal to the average atmospheric pressure at sea level.
- Bar: Equal to 100,000 Pascals.
Examples of Pressure Calculation
-
Example 1: A 100 N force is applied to an area of 2 m². What is the pressure?
- p = F/A = 100 N / 2 m² = 50 Pa
-
Example 2: A person weighing 700 N stands on a rectangular block that is 0.5 m long and 0.2 m wide. What is the pressure exerted on the ground?
- A = length width = 0.5 m 0.2 m = 0.1 m²
- p = F/A = 700 N / 0.1 m² = 7000 Pa
Key Takeaways
- Pressure is force distributed over an area.
- The formula
p = F/Ais fundamental for calculating pressure. - Understanding the relationship between force, area, and pressure is crucial in various fields, including engineering, physics, and everyday life.
