Which among the following is (are) the unit of pressure? (1) \(\mathrm{N} \mathrm{m}^{-2}\) (2) \(\mathrm{gwt} \mathrm{cm}^{-2}\) (3) kgwt \(\mathrm{m}^{-2}\) (4) All the above

Understanding what pressure means in physics is crucial for many applications, from checking your car's tires to measuring atmospheric conditions. Pressure is simply the amount of force exerted over a specific area. When you press your hand against a wall, you're applying force to the wall, and this force spread over the area of your hand that touches the wall represents pressure.

Imagine you're using your finger to push a pushpin into a notice board. Even though the force you exert is relatively small, the area over which it is applied is tiny (the tip of the pin), so the resulting pressure is high enough to push the pin into the board. On the other hand, if you were to press the flat side of your hand against the pin, even with the same force, you wouldn't be able to push it in because the area is much larger, resulting in lower pressure.

Let's delve deeper into the fundamental principle of pressure—force per unit area. It's a straightforward concept: pressure increases if you apply the same force over a smaller area, and pressure decreases when you spread that force out over a larger area. The formula to calculate pressure is thus given by:

\[\begin{equation}Pressure = \frac{Force}{Area}\end{equation}\]

In this equation, 'Force' stands for the push or pull you're exerting on an object, measured in Newtons (N) for SI units. The 'Area' is the surface area over that force is distributed, measured in square meters (\[\begin{equation}\mathrm{m}^2\end{equation}\]).

Real-World Application

Consider a snowshoe: its wide base spreads the force exerted by your weight over a larger area, reducing the pressure on the snow and preventing you from sinking. That's the force per unit area concept in action.

The SI (International System of Units) unit of pressure is the pascal (Pa). This unit is named after Blaise Pascal, a French mathematician, physicist, and inventor, who did significant work in the field of hydrodynamics and hydrostatics and the study of fluids. One pascal is defined as one newton per square meter (\[\begin{equation}1\;Pa = 1\;N/m^2\end{equation}\]).

While the pascal is the standard unit of pressure in the SI system, various other units are used in different contexts, such as the bar (used in meteorology) or the atmosphere (atm), which is used to describe the pressure exerted by the Earth's atmosphere at sea level. Additionally, pressure can also be measured in terms of the weight of an object. For example, the gram weight per square centimeter (\[\begin{equation}\mathrm{gwt} \; \mathrm{cm}^{-2}\end{equation}\]) or the kilogram weight per square meter (\[\begin{equation}\mathrm{kgwt} \; \mathrm{m}^{-2}\end{equation}\]) are both valid units that express pressure.