The load required to produce a unit deflection in a spring is called spring stiffness.

Atmospheric pressure: The atmospheric air exerts a normal pressure upon all surfaces with which it is in contact and it is known as atmospheric pressure. Atmospheric pressure is also known as barometric pressure. The atmospheric pressure at sea level (above absolute zero) is called standard atmospheric pressure and its value is given as follows:

Standard atmospheric pressure = 101.3 kN/m² or kPa (1 kN/m² = 1 kPa)
= 10.3 m of water
= 760 mm of Hg
Atmospheric pressure = Absolute pressure - Gauge pressure