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Effect of Earth's rotation on g
Intermediate
g is smaller at the equator due to centrifugal effect.
g' = g − ω²R cos²λRotation reduces effective gravity by the centrifugal term ω²R cos²λ. It's zero at the poles and about 0.034 m/s² at the equator. Also, Earth bulges at the equator.
Apparent weight is 0.3% less at the equator.
The effect is small but measurable.
In more detail
Earth's rotation reduces the apparent weight of objects at the equator, because part of the gravitational pull provides centripetal acceleration. The effect is largest at the equator and zero at the poles.
Real-world uses
- Rockets launch eastward to gain speed from Earth's rotation.
- Precision geodesy corrects measured g for Earth's spin.
- Engineers include the Earth's rotation when calibrating precise gravimeters, since g is slightly smaller at the equator.
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Frequently asked questions
Would I weigh less at the equator?
Slightly, about 0.3% less, due to Earth's rotation.
Why is the effect zero at the poles?
Because a point on the axis has no circular motion, so no centripetal acceleration is needed.
Why is my weight slightly lower at the equator?
Earth's rotation provides a centripetal requirement, so the effective pull is reduced slightly there.
Related topics in Gravitation & Orbits
Acceleration due to gravity · Variation of g with altitude · Variation of g with depth · Gravitational field · Gravitational potential energy · Gravitational potential