Tyngdeacceleration

Tyngdeacceleration, or gravitational acceleration, is the acceleration a body experiences due to gravity in the vicinity of a massive body such as Earth. It is commonly denoted by g and measured in meters per second squared (m/s^2). Near the Earth's surface, g is about 9.81 m/s^2 in a vacuum, but it varies with location and altitude.

g is defined as the acceleration of a freely falling object, ignoring air resistance. In vector form it points toward the center of the Earth, and its magnitude changes with distance from the planet according to an inverse-square relation for a roughly spherical body. The standard gravity, g0, is defined as 9.80665 m/s^2.

In practice, g varies with altitude, latitude, and local mass distribution. At higher elevations, g decreases roughly as 1/(R + h)^2, where R is the planet’s mean radius and h is height above the surface. Latitudinal variation arises from the planet’s rotation, which produces centrifugal acceleration that reduces the net g felt at the equator compared with the poles.

g is related to weight by W = m g, where m is mass. It is the acceleration component caused by gravity alone and is distinct from other accelerations acting on a body, such as air drag or propulsion. Measurements of gravitational acceleration are used in geophysics, engineering, and navigation, and the value of g differs on other bodies—Moon about 1.62 m/s^2, Mars about 3.71 m/s^2, and so on.