If some object is weighed when submerged in water

GP Solids Fluids

If some object is weighed when submerged in water, what will happen to its weight compared to its weight in air?

  1. Increase
  2. Decrease
  3. Remain exactly the same
  4. Increase or decrease cannot be predicted

Answer

The weight of an object is defined by its mass multiplied by the acceleration due to gravity.

w = mg

An object weighs the same in air as well as in water. But, in water an additional buoyant force acts on the ball in a direction opposite to the direction in which the weight of the ball acts. If the weight of the ball acts downwards, buoyant force acts upwards. These two forces work together to make it seem as the object weighs less in water.

In air, due to very low density of air, the buoyant force acting on the object is almost negligible.

Archimedes' principal states that the magnitude of the upward force an object immersed in a fluid experiences is equal to the weight of the fluid displaced due to that object. 

m = density × volume

w = density × volume × acceleration due to gravity

The correct option is A.