Physics 2001 JAMB Past Questions - Question 7: I. The earth is not spherical but elliptical in shape. II. Variation in latitude and longitude. III. Rotation of the earth on its axis. IV. Variation in the density of the earth. On which combination of the above does the weight of an object vary on the earth's surface?

Correct Answer

C

Explanation

The weight of an object on the Earth's surface varies primarily due to variations in two factors:

I. The earth is not spherical but elliptical in shape: The Earth is not a perfect sphere, but rather an oblate spheroid, meaning it's slightly flattened at the poles and bulging at the equator. This variation in shape can lead to slight variations in gravitational force and, therefore, the weight of objects at different locations on the Earth's surface.

III. Rotation of the earth on its axis: The Earth's rotation causes variations in the gravitational force, leading to differences in weight. The centrifugal force generated by the Earth's rotation causes objects at the equator to weigh slightly less than objects at the poles. This is due to the fact that the Earth's equatorial regions are farther from its center of mass due to the bulging effect.

The variation in latitude and longitude (II) doesn't directly affect an object's weight, but it can affect its position on the Earth's surface.

Variation in the density of the Earth (IV) does not play a significant role in variations in the weight of an object on the Earth's surface. The density of the Earth's interior is relatively consistent on a global scale, and local variations in density have minimal impact on an object's weight.

So, the combination of factors I and III contributes to the variation in the weight of an object on the Earth's surface.