Question

A body is just floating on the surface of a liquid. The density of the body is same as that of the liquid. The body is slightly pushed down. What will happen to the body?

• A. It will slowly come back to its earlier position
• B. It will remain floating where it was left
• C. It will sink
• D. It will come out violently

Answer 1

The correct option is

B

It will remain floating where it was left

$Mg={\rho }_{B}Vg$

$F_B={\rho }_{\omega }Vg$

Given ${\rho }_B={\rho }_{\omega }$

$\Rightarrow Mg=F_B$

This implies that buoyant force will always be equal to the force of gravity which means, it will be in a state of equilibrium even when completely submerged.

Even when it is slightly pushed down, it will still remain in equilibrium. The buoyant force can never be greater than mg, therefore, the block will just remain there.