An object placed on water surface will sink if ________.

Concept:

Archimedes principle:

• The principle of Archimedes states “When a body is immersed in a liquid, an upward thrust, equal to the weight of the liquid displaced, acts on it.”

• Thus, when a solid is fully immersed in a liquid, it loses weight which is equal to the weight of the liquid it displaces.

i.e., 

\(\Rightarrow Apperent\;weight = actual\;weight - buoyant\;force = mg - \rho gV\)

Here, m is mass of the object, ρ = density of the liquid, g = acceleration due to gravity, and V = volume of liquid displaced by the object

• Hence if there is no gravity, there is no Upward Thrust.
• The upward force applied on the object is called buoyant force or upward thrust or buoyancy of liquid.

Explanation:

• From the above explanation, we can see that the upward thrust or buoyant force exerted by the liquid is completely responsible for the floatation of an object on any liquid surface.
• And thus, an object placed on the water surface will sink if the weight of the object is greater than the buoyancy of the liquid

i.e., The weight of an object > the buoyancy of water