SSC JE Civil Engineering 23-Mar-2021 Shift 2 Paper

Here we are neglecting the buoyant force due to air and only buoyant force due to water is considered.
Weight of stone in air, W = 250 N
(W = mg); m is the mass and g is acceleration due to gravity
Weight of stone in water, ${\mathrm{W}}_{\mathrm{w}}=150\mathrm{N}$
Total Force on stone, when it is submerged in water fully,
$\mathrm{F}=\mathrm{mg}-{\mathrm{\gamma }}_{\mathrm{w}}\times {\mathrm{V}}_{\mathrm{sub}}$
Since stone is fully submerged so its submerged volume is the volume of stone i.e. ${\mathrm{V}}_{\mathrm{sub}}=\mathrm{V}$
Now,
$\mathrm{F}={\mathrm{W}}_{\mathrm{w}}=150\mathrm{N}$ (Given)
$\mathrm{Mg}={\mathrm{W}}_{\mathrm{w}}=250\mathrm{N}$ (Given)
Putting these values, we get
$150=250-10000\times \mathrm{V}$
$\therefore \mathrm{V}=0.01{\mathrm{m}}^3$