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The magnitude of the effect depends on the air density (and hence air pressure) or the water density respectively; see Apparent weight for details. The gravitational effects of the Moon and the Sun (also the cause of the tides ) have a very small effect on the apparent strength of Earth's gravity, depending on their relative positions; typical ...
where and are ambient pressure and temperature, respectively, as functions of geopotential height, and is the specific gas constant. For the subsequent definite integral , the simplification obtained by assuming a constant value of gravitational acceleration is the sole reason for defining the geopotential altitude.
It is a constant defined by standard as 9.806 65 m/s 2 (about 32.174 05 ft/s 2). This value was established by the third General Conference on Weights and Measures (1901, CR 70) and used to define the standard weight of an object as the product of its mass and this nominal acceleration .
Pressure as a function of the height above the sea level. There are two equations for computing pressure as a function of height. The first equation is applicable to the atmospheric layers in which the temperature is assumed to vary with altitude at a non null lapse rate of : = [,, ()] ′, The second equation is applicable to the atmospheric layers in which the temperature is assumed not to ...
When density and gravity are approximately constant (that is, for relatively small changes in height), simply multiplying height difference, gravity, and density will yield a good approximation of pressure difference. If the pressure at one point in a liquid with uniform density ρ is known to be P 0, then the pressure at another point is P 1:
At a fixed point on the surface, the magnitude of Earth's gravity results from combined effect of gravitation and the centrifugal force from Earth's rotation. [2] [3] At different points on Earth's surface, the free fall acceleration ranges from 9.764 to 9.834 m/s 2 (32.03 to 32.26 ft/s 2), [4] depending on altitude, latitude, and longitude.
The specific weight, also known as the unit weight (symbol γ, the Greek letter gamma), is a volume-specific quantity defined as the weight W divided by the volume V of a material: = / Equivalently, it may also be formulated as the product of density, ρ, and gravity acceleration, g: = Its unit of measurement in the International System of Units (SI) is newton per cubic metre (N/m 3), with ...
= pressure . In meteorology, and are isobaric surfaces. In radiosonde observation, the hypsometric equation can be used to compute the height of a pressure level given the height of a reference pressure level and the mean virtual temperature in between. Then, the newly computed height can be used as a new reference level to compute the height ...