Question

An object weighs \[500\,g\] in air. What is its probable weight when it is fully immersed in water?
A. $365\,g$
B. $500\,g$
C. $575\,g$
D. $800\,g$

Answer 1

Hint: The given question is based on the concept of Archimedes principle, so we will go through the same principle to know whether the weight is less, equal or greater than the given weight of an object in air. As the buoyant force in air is lower than the buoyant force in water.

Complete step by step answer:
When a body is submerged in water, a buoyant force acts upward on it. The size of this buoyant force on a body in various media is determined by the media's densities.The density of air is lower than that of water. As a result, the buoyant force in air is substantially lower than the buoyant force in water. As a result, the weight loss in water is substantially more than the weight loss in air. It will weigh less in water because the weight decreases more in water.

Or in other words- in air, there is a buoyant force equal to the mass of air displaced by the object, as well as an equal and opposing force of the object's weight if the object is on a horizontal surface (normal force). In water, there is also a buoyant force equal to the mass of the water displaced by the object pushing up on the object, as well as a normal force if the object is resting on a horizontal surface, according to Archimedes' principle.

However, because air is less thick than water, its buoyant force is lower, making an object in air appear heavier.Therefore, only option (A) $365\,g$ is less than the actual weight of an object in the air. So, $365gm$ may be probably the weight of an object when it is immersed in water.

Hence, the correct option is A.

Note: When the body is submerged in water, upthrust acts vertically upward, reducing the downward force on the body; but, when the body is submerged in air, upthrust is minimal or equal to weight, hence weight is greater.