The equation for measuring apparent weight is F = mg + ma. F represents apparent weight in newtons, m is the mass of the object, g is the acceleration due to gravity (9.8 meters per second squared on Earth's surface) and a is the acceleration of the object.
The apparent weight of an object when it is at rest, free falling or moving at constant speed is equal to its normal weight because the object's acceleration is zero. When the object is moving upward, for example in an elevator, the object's apparent weight is heavier. This is due to the additional force necessary to push the object up, represented by mass times acceleration with positive acceleration value. If the object is moving downward, its apparent weight is lighter, since the object is actually decelerating and thus has a negative acceleration value.