Question

A metal cube is placed in an empty vessel. When water is filled in the vessel so that cube is completely immersed in the water, the force on the bottom of the vessel in contact with the cube-

• A. Will increase
• B. Will decrease
• C. Will remain the same
• D. Will become zero

Answer 1

The correct option is C Will remain the same

If the height of water is equal to the height of the metallic cube and no mass of water is above the cube then the net force on the base, in contact with cube will not change.

However, if you fill the water to a certain height $\left(h\right)$ above the cube to make it completely immersed, then the force on the bottom (in contact with the cube) will increase by $\rho ghA$.

Where $\rho$=density of water

$g$ = acceleration due to gravity

$A$ = contact area of base of the cube

It doesn't matter if the cube floats, suspends in the middle or remains in its place. Unless it doesn't move laterally the pressure will not vary, as net mass of the liquid and block above the contact area remains the same.