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Acceleration due to gravity
Beginner
Field strength at Earth's surface.
g = GM/R²At a planet's surface g = GM/R². It does not depend on the falling mass. For Earth g ≈ 9.8 m/s²; on Mars about 3.7.
Mass and radius of the Moon give g ≈ 1.6 m/s².
g varies with location; G does not.
In more detail
The acceleration due to gravity at a planet's surface is g = GM/R². It depends on the planet's mass and radius, so it differs from one world to another.
Real-world uses
- Mars has about 0.38 g, so jumps and falls are different there.
- Estimating surface gravity on exoplanets from their mass and radius.
- Surveyors and geophysicists measure small variations in g to find buried rock or mineral deposits.
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Frequently asked questions
Is g the same for all objects?
Yes, in a given location, all objects accelerate at g if air resistance is ignored.
What is g at Earth's surface?
About 9.8 m/s² on average.
Is g the same everywhere on Earth?
No. It varies by about half a percent, depending on altitude, latitude and local rock density.
Related topics in Gravitation & Orbits
Universal law of gravitation · Gravitational constant G · Variation of g with altitude · Variation of g with depth · Effect of Earth's rotation on g