In flight mechanics, the hydrostatic equation refers to a fundamental principle in fluid mechanics that describes the variation of pressure with height (altitude) in a static fluid, such as the Earth’s atmosphere. This equation is based on the concept of hydrostatic equilibrium, which means that the pressure at any point in a fluid is in balance with the weight of the fluid above it.
dp/dh=ρ⋅g
represents the hydrostatic equation in a slightly different form, where ℎ is the rate of change of pressure with respect to altitude ℎ, is the density of the fluid (usually air) at the given altitude, and is the acceleration due to gravity.