Question

If the relative density of an object $\left({\rho }_r\right)$ is $0.6$ and volume $\left(V\right)$ is $1.5m^3$. Calculate the mass $M$ of the object.
Given, density of water, ${\rho }_w=1000kg{m}^{-3}$

• A. $900kg$
• B. $600kg$
• C. $400kg$
• D. $1200kg$

Answer 1

The correct option is A $900kg$

Given:
Density of water: ${\rho }_w=1000kg{m}^{-3}$
Volume of object: $V=1.5m^3$
Relative density of object: ${\rho }_r=0.6$

Let the absolute density of the object be $\rho$.
​​From definition of relative density,
${\rho }_r=\frac{\rho }{{\rho }_w}$
$\rho ={\rho }_r{\rho }_w$
$\rho =0.6\times 1000=600kg{m}^{-3}$

From defintion of density,
$M=\rho V$
$M=600\times 1.5=900kg$