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# Units of pressure

The SI unit of pressure is the pascal $(\text{Pa})$ which is defined as

$$\Torange{\text{Pa}}= \dfrac{\Tblue{\text{N}}}{\Tred{\text{m}^{2}}} = \dfrac{\Tblue{\text{kg m/s}^{2}}}{\Tred{\text{m}^{2}}} = \dfrac{\Torange{\text{kg}}}{\Torange{\text{m s}^{2}}}$$

It is also common to use other (non-SI) units to express pressure:

• The atmosphere ($1\text{ atm}=101.325 \text{ kPa}$), which is equivalent to the standard atmospheric pressure.

• The bar ($1\text{ bar}=10 ^{5} \text{ Pa}$) which is very close to the standard atmospheric pressure ($1\text{ atm}$).

Example Pressure (estimation)
Pressure in a vacuum $0\text{ Pa}$
Blood pressure of healthy adult at rest $16\text{ kPa}$
Atmospheric pressure $100\text{ kPa}$
Water pressure of a garden hose $300\text{ kPa}$
Pressure of the average human bite $1.10\text{ MPa}$