Worked Examples-Calculation Part 1 - Pressure

Considered Formula

$$P = \frac{F}{A}$$ $$\text {Where}~~P \to Pressure,~~~~~ F \to Force ~~~~~ A \to Area$$

Example 1

A log exerts weight of 1200 N on the ground at an area of 8 m². Calculate the pressure exerted by the log to the ground.

Solution

Data given

Force (F) = 1200 N

Area (A) = 8 m²

Pressure (P) =?

$$~~~~~~~~~~~~~~~~~~~~~~~~~~~~P = \frac{F}{A}$$ $$~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ = \frac{1200}{8}$$ $$~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ = 150~N/m^2$$

The pressure exerted by the log to the ground = 150 N/m²

Example 2

A doctor applies a force of 80 N to tip a victim. If the surface area of the needle used in syringe was 0.0002 m². Calculate the pressure exerted by needle the skin of the victim.

Solution

Data given

Force (F) = 80 N

Area (A) = 0.0002 m²

Pressure (P) =?

$$~~~~~~~~~~~~~~~~~~~~~~~~~~~~P = \frac{F}{A}$$ $$~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ = \frac{80}{0.0002}$$ $$~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ = 400,000~N/m^2$$

The pressure exerted by needle = 400,000 N/m²