Question

The Earth's gravitational acceleration is higher at the poles compared to that at the equator due to

• A. higher density rocks at the poles
• B. shorter polar radius
• C. lower centrifugal acceleration at the poles
• D. higher topography at the poles

Hint:

Gravitational acceleration is higher at the poles primarily due to the Earth's shape (shorter polar radius) and the fact that centrifugal force is minimized there.

Answer 1

The Correct Option is B

Step 1: What sets surface gravity.
Gravity at the surface grows when you sit closer to the Earth centre, since it falls off with distance squared.

Step 2: The shape of the Earth.
The Earth is not a perfect ball. It bulges at the equator and is flattened at the poles, so the polar radius is shorter.

Step 3: Link shape to gravity.
Because the poles are nearer the centre, the pull there is a bit stronger. This shorter polar radius is the main reason gravity is higher at the poles.

Step 4: Weigh the other options.
The spin does reduce gravity more at the equator, and rock density and topography play small parts, but the leading cause is the shorter polar radius.

Step 5: Final choice.
So the main reason is the shorter polar radius.
\[ \boxed{\text{shorter polar radius}} \]