Question

A block of wood is floating on oil with half of its volume submerged. If the density of oil $840kg{m}^{-3}$, the relative density of wood (relative to water) is:

• A. 0.84
• B. 0.42
• C. 0.21
• D. 1

Answer 1

The correct option is B 0.42

${\varrho }_w{V}_w={\varrho }_{oil}\times V_{submerged}$

${\varrho }_w\times \frac{V_w}{2}={\varrho }_{oil}\times \frac{V_w}{1}$

${\varrho }_w=\frac{840}{2}=420kg/m^3$

So relative density = $\frac{densityofwood}{densityofwater}$

= 0.42