Question

The SI unit of pressure is______.
$\text{A}\text{. }\dfrac{N}{{{m}^{2}}}$
$\text{B}\text{. }Pa$
C. Both A and B
D. None of the above

Answer 1

Hint: To find the SI unit of pressure, we will apply the formula for pressure relating applied force and the area associated with that force. The SI units of Force and Area on division will give the SI unit of Pressure.

Formula used:
$\text{Pressure = }\dfrac{\text{Force}}{\text{Area}}$

Complete step by step answer:
Pressure is defined as the physical force exerted on an object. The force applied is perpendicular to the surface of objects per unit area.

The basic formula for pressure is Force per unit area.
$P=\dfrac{F}{A}$
Where,
$P$ is the pressure
$F$ is the magnitude of the normal force
$A$ is the area of surface in contact
The pressure is a scalar quantity, and does not have any direction. It is incorrect to say that the pressure is directed in such or such direction. The force has a direction, but the pressure does not.
Calculating SI unit of Pressure,
We have the formula $P=\dfrac{F}{A}$
SI unit of Force $(F)$ is Newton $(N)$
SI unit of Area $(A)$ is ${{m}^{2}}$
Therefore, we get
$P=\dfrac{\text{Force }(N)}{\text{Area }({{m}^{2}})}$
We get, SI unit of pressure is $\dfrac{N}{{{m}^{2}}}$
Pascal $(Pa)$ is the coherent derived unit of pressure and accepted as the SI unit of pressure. 1 Pascal is equal to$1\text{ }N{{m}^{-2}}$.
Hence, the correct option is C.

Additional information:
The CGS unit of pressure is barye $(Ba)$, which is equal to 1 dyne per square centimetre. Dyne is the CGS unit of Force. 1 Dyne is equal to the force which is required to accelerate mass of one gram to a rate of one centimetre per second per square.
$barye=\dfrac{dyne}{c{{m}^{2}}}$
1 barye is equal to 0.1 Pascal.
$1\text{ }Ba=0.1\text{ }Pa$

Note: Students should remember the SI units of Force and Area to calculate the SI unit of Pressure. Also, Pressure is the normal force per unit area and it is a scalar quantity having no direction. Both Pascal and $N{{m}^{-2}}$ are considered as the SI units of pressure.