(i) Pressure in solids
Pressure is defined as the amount of force exerted (thrust) on a surface per unit area. It can also be defined as the ratio of the force to the area (over which the force is acting). Therefore, pressure can be represented by the equation:

Note that pressure is directly proportional to force and inversely proportional to area. Thus, pressure can be increased either by increasing the amount of force or by decreasing the area over which it is applied. The pressure of a solid arises due to the weight of the solid.

The units of pressure are derived from the units used to measure force and area. Force is measured in newton (N) and area is measured in square meters (m²). Therefore, pressure is expressed in N/m², which is called the Pascal (Pa), after the French
mathematician Blaise Pascal (1623–1662). Other units include the atmosphere (atm). Pressure is a scalar quantity. Pressure may also be expressed in the kilopascal (kPa), which equals 1000 Pascal.

Since pressure has only a magnitude, no direction, it is a scalar quantity.