At which place on the Earth's surface is the gravitational force experienced by objects maximum?

Introduction / Context:
The strength of gravitational force experienced at the Earth's surface is not exactly the same everywhere. It varies slightly due to the planet's shape and rotation. Understanding where gravity is maximum is a basic but important concept in physical geography and physics. This question checks whether you know the relationship between latitude, Earth's rotation, its equatorial bulge and how these affect the value of acceleration due to gravity at different locations such as the equator and the poles.

Given Data / Assumptions:
- Four possible locations are given: equator, Tropic of Cancer, Tropic of Capricorn and the poles. - We assume a basic model of the Earth as an oblate spheroid that rotates on its axis. - Variations in gravitational force are small but measurable. - We neglect local geological anomalies and focus on the general latitudinal pattern.

Concept / Approach:
Two main factors cause variation in gravity: the Earth's rotation and its shape. Rotation produces a centrifugal effect that is greatest at the equator and zero at the poles. This effectively reduces the apparent gravity at the equator. The Earth is also slightly flattened at the poles and bulged at the equator, so the polar radius is smaller. Since gravitational force is stronger at smaller distances from the centre of mass, being physically closer at the poles increases gravity. Combined, these effects mean that the value of acceleration due to gravity is maximum at the poles and minimum at the equator.

Step-by-Step Solution:
Step 1: Recall that centrifugal effect due to rotation is highest at the equator, reducing effective gravity there. Step 2: Recognise that centrifugal effect is zero at the poles, so gravity is not reduced by rotation at those points. Step 3: Understand that the Earth's equatorial bulge makes the equatorial radius larger, so the equator is farther from the Earth's centre. Step 4: At the poles, the radius is smaller, so the distance to the centre is less and the gravitational pull is stronger. Step 5: Therefore, among the given options, gravitational force is maximum at the poles.

Verification / Alternative check:
Standard physics and geography texts often present numerical values of acceleration due to gravity: approximately 9.78 m/s^2 at the equator and about 9.83 m/s^2 at the poles. Even without remembering exact numbers, you can remember the qualitative rule that gravity increases from the equator towards the poles. The Tropic of Cancer and Tropic of Capricorn lie between the equator and poles, so gravity there is intermediate. Since the question asks for the maximum value, the poles must be chosen.

Why Other Options Are Wrong:
At the equator, gravity is least because both the larger radius and maximum centrifugal effect reduce effective gravitational pull.
At the Tropic of Cancer, gravity is higher than at the equator but still lower than at the poles, so it cannot be the maximum value on Earth.

At the Tropic of Capricorn, the situation is similar to the Tropic of Cancer; gravity is intermediate, not maximum, because the latitude is not as high as the poles.

Common Pitfalls:
A frequent mistake is to assume gravity must be highest where the Earth rotates fastest, leading to the wrong idea that the equator has maximum gravity. Another common confusion is between mass and weight; gravity does not change the mass of an object, only its weight. Remembering the link between distance from the Earth's centre and gravity, as well as the diminishing centrifugal effect toward the poles, helps avoid these misconceptions.

Final Answer:
The gravitational force acting on objects at the Earth's surface is maximum at the poles.