Question

At which place on the Earth's surface is the acceleration due to gravity maximum, the poles or the equator?

Hint:

Compare the Earth's radius at the poles with its radius at the equator, and remember g depends on 1 over R squared.

Answer 1

Step 1: The Earth is not a perfect sphere. It is flattened at the poles and bulges out at the equator, so the equatorial radius is slightly larger than the polar radius.

Step 2: The acceleration due to gravity at the surface is given by \( g = \dfrac{GM}{R^2} \), where \( R \) is the distance from the centre of the Earth to that point on the surface.

Step 3: Since \( g \) is inversely proportional to \( R^2 \), a smaller radius gives a larger value of \( g \). The polar radius is smaller than the equatorial radius, so \( g \) is larger at the poles.

Step 4: There is also a smaller effect from the Earth's rotation. At the equator the spinning motion reduces the effective weight of a body, while at the poles this effect is zero, which again makes \( g \) larger at the poles.

Answer: The acceleration due to gravity, and hence the gravitational pull felt by an object, is maximum at the poles.