The Earth's gravitational acceleration is higher at the poles compared to that at the equator due to
Show Hint
- higher density rocks at the poles
- shorter polar radius
- lower centrifugal acceleration at the poles
- higher topography at the poles
The Correct Option is B
Solution and Explanation
Gravitational acceleration at the Earth's surface is influenced by two primary factors: the mass distribution of the Earth and the distance from the Earth's center. The acceleration due to gravity is stronger when the distance from the Earth's center is smaller.
Step 2: Analyzing the effect of the Earth's shape.
The Earth is not a perfect sphere but an oblate spheroid, meaning it is slightly flattened at the poles and bulging at the equator. As a result, the polar radius (the distance from the Earth's center to the poles) is shorter than the equatorial radius (the distance from the Earth's center to the equator).
Since gravitational acceleration is inversely proportional to the square of the distance from the Earth's center, gravity is stronger at the poles, where the distance is shorter. This is why gravitational acceleration is higher at the poles.
Step 3: Analyzing the other options.
- Option (A): Higher density rocks at the poles: While density variations in the Earth's crust exist, they do not significantly affect gravitational acceleration in comparison to the effect of radius.
- Option (C): Lower centrifugal acceleration at the poles: The centrifugal force due to Earth's rotation is lower at the poles (because the rotational speed is zero at the poles), but this has a minor effect compared to the radius factor.
- Option (D): Higher topography at the poles: Topography does influence local gravity slightly, but the primary factor for the difference in gravitational acceleration between the poles and the equator is the radius, not topography.
Step 4: Conclusion.
The correct answer is (B) shorter polar radius, as this leads to stronger gravitational acceleration at the poles due to the reduced distance from the Earth's center.
\[ \boxed{\text{shorter polar radius}} \]
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