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Gravitational force is the attractive force that the Earth exerts on objects. It pulls objects towards its center and is given by the formula:

• \( F_g = mg \), where \( F_g \) is the gravitational force, \( m \) is the mass of the object, and \( g \) is the acceleration due to gravity.

This force is what we commonly refer to as "weight." Imagine a magnet attracting a metal piece—gravity does something similar by pulling everything towards Earth.
When you stand on a scale, the scale measures this gravitational force acting on your body. That's why your scale reading reflects your weight. In our scenario, the gravitational force is the same whether Earth rotates or not. However, the scale reading might not always match the gravitational force exactly if other forces, like centrifugal force, are involved.Understanding gravitational force helps us unravel why scales show a different reading when Earth's rotation comes into play. The gravitational force remains constant, but how it's balanced or appears to be balanced (apparent weight) by other forces varies.

Normal force is the support force exerted by surfaces perpendicular to the surface. When you stand on a scale, the scale provides an upward force equal to your gravitational force, which we call the normal force.
It counteracts the force of gravity, ensuring that you remain in equilibrium and do not fall through the scale. Since the scale shows the force it exerts (the normal force), in the absence of other active forces, it reflects the gravitational force directly. However, if the Earth's rotation is considered, a small reduction occurs in the normal force due to the centrifugal force acting outward, which we will explore in the next section. This slight reduction is what makes the scale read less than the gravitational force under normal circumstances. But if Earth did not rotate, this centrifugal effect wouldn't exist, and the normal force would be unrestricted by any reducing factors, resulting in a higher reading on the scale.

The Earth's rotation introduces an interesting, albeit slightly complex, force called centrifugal force. This force acts outward from the axis of rotation. Due to Earth's fast spin, centrifugal force affects objects on its surface, including you, by slightly reducing the apparent weight measured by a scale.
This happens because while the gravitational force pulls you down, the centrifugal force tries to push you away from the axis of rotation. It slightly counteracts gravity, diminishing the normal force exerted by the Earth. Thus, the scale displays a lower weight than your true gravitational weight. If Earth stopped rotating, the centrifugal effect would vanish. Without anything opposing the gravitational pull, the normal force would fully balance the gravitational force without any reduction. This makes scales show the complete gravitational weight, producing a higher reading compared to a rotating Earth scenario.