Explanation:

The weight of an object is given by the formula $W = mg$, where $m$ is its mass and $g$ is the acceleration due to gravity. The value of $g$ varies across the Earth's surface. Due to the Earth's rotation and its oblate spheroid shape (it bulges at the equator and is flattened at the poles), the acceleration due to gravity is maximum at the poles and minimum at the equator. At the poles, an object is closest to the Earth's center of mass, and the centrifugal force due to rotation is zero. At the equator, an object is farthest from the center and experiences the maximum outward centrifugal force. The Tropics of Capricorn and Cancer are intermediate latitudes between the equator and the poles, where $g$ would be between its maximum and minimum values. Therefore, the weight of an object is maximum at the poles.