The Earth’s oblate shape causes gravitational acceleration to be slightly stronger at the poles than at the equator, increasing a body’s weight when moved poleward.
Class 11 Physics
Gravitation
CBSE EXAM 2024-25
Discuss the variation of g on earth’s surface due to shape of the earth. Why does the weight of a body increase when it is taken from the equator to the pole?
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Effect of the Earth’s Shape on g:
The Earth is not a perfect sphere; it is slightly flattened at the poles and bulges at the equator. This means the equatorial radius of the Earth is about 21 km greater than the polar radius.
Since the acceleration due to gravity is inversely proportional to the square of the radius g ∝ 1/R² , the larger radius at the equator results in a lower value of g , while the smaller radius at the poles leads to a higher value of g.
Thus, gravity is minimum at the equator and maximum at the poles. This explains why the weight of an object increases when it is moved from the equator to the poles. The variation in g between the poles and the equator is approximately 0.5%.