Gravity of Earth
The gravity of Earth, denoted by g, is the net acceleration that is imparted to objects due to the combined effect of gravitation and the centrifugal force.
It is a vector quantity, whose direction coincides with a plumb bob and strength or magnitude is given by the norm g = ‖ g ‖. In SI units, this acceleration is expressed in metres per second squared or equivalently in newtons per kilogram. Near Earth's surface, the acceleration due to gravity, accurate to 2 significant figures, is 9.8 m/s⁲ (32 ft/s⁲). This means that, ignoring the effects of air resistance, the speed of an object falling freely will increase by about 9.8 metres per second (32 ft/s) every second. This quantity is sometimes referred to informally as little g. The precise strength of Earth's gravity varies with location. The agreed upon value for standard gravity is 9.80665 m/s⁲ (32.1740 ft/s⁲) by definition. This quantity is denoted variously as gn, ge, g0, or simply g. The weight of an object on Earth's surface is the downwards force on that object, given by Newton's second law of motion, or F = m a. Gravitational acceleration contributes to the total gravity acceleration, but other factors, such as the rotation of Earth, also contribute, and, therefore, affect the weight of the object. Gravity does not normally include the gravitational pull of the Moon and Sun, which are accounted for in terms of tidal effects.
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