Scientific

Standard Gravity

Definition

The nominal gravitational acceleration at Earth’s surface, defined exactly as 9.80665 m/s², used to define the kilogram-force and standardize weight measurements.

Explanation

Actual surface gravity varies from 9.764 m/s² at the equator to 9.863 m/s² at the poles due to Earth’s rotation and non-spherical shape. The standard value of 9.80665 m/s² was adopted in 1901 to provide a consistent reference for force unit conversions: one kilogram-force equals exactly 9.80665 newtons. Spring scales calibrated for standard gravity will read about 0.5% high at the equator.

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