why body weighs slightly less at the equator compared to the North and south Poles
Body weighs slightly less at the equator compared to the North Pole and south pole. This difference in weight is due to the variation in gravitational acceleration caused by the Earth's shape and rotation. Here's why:
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Earth's Oblate Spheroid Shape: The Earth is not a perfect sphere but rather an oblate spheroid, which means it is slightly flattened at the poles and bulging at the equator. This shape results from the Earth's rotation. The equatorial radius (distance from the Earth's center to the equator) is greater than the polar radius (distance from the Earth's center to the North or South Pole).
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Gravitational Acceleration: Gravitational acceleration (often denoted as "g") depends on the distance between an object and the center of the Earth. Because the Earth is not a perfect sphere, the distance from the center of the Earth to a point on its surface varies. It is greater at the equator than at the poles.
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Weight Calculation: Your weight is a force caused by the gravitational pull of the Earth. It is calculated using the formula: Weight (W) = mass (m) × gravitational acceleration (g).
Since "g" is greater at the poles due to the shorter distance to the center of the Earth and smaller at the equator due to the greater distance, your weight will be slightly less at the equator.
However, the difference is very small. On average, your weight at the equator is only about 0.5% less than your weight at the North Pole. It's not something you'd notice without highly precise instruments. The variations in weight due to changes in altitude (distance from the Earth's surface) and the local geology (density of the Earth's crust) can also have a more significant impact on your weight than the equator-pole difference.