(4) Weight of a body is the force experienced by the body due to gravity. if the body is in air, the buoyant force of the air reduces its weight. A body weighed in vacuum will show a slight increase in the weight of the body. A human body has roughly neutral buoyancy in water. The density of air is about 1/1000 that of water about 1gram per litre. So if the person weighs W kilos in air,then in a vacuum deprived of that buoyancy, he’ll weigh W grams more.’