Question

A glass flask having mass $390g$ and an interior volume of $500c{m}^3$ floats on water when it is less than half filled with water. The density of material of the flask is

• A. 0.8 g/cc
• B. 2.8 g/cc
• C. 1.8 g/cc
• D. 0.28 g/cc

Answer 1

Answer: (B)

As the flask floats in water when less than half filled with water, it will float just fully submerged when half filled.
In this situation, mass of flask + mass of water in it
$=V\sigma ie,390+250=V\times 1(as\sigma =1g/cc)$

i.e, outer volume of flask
$V=640cc$
Now as inner volume of flask is given to be $500cc$, so the volume of the material of flask $=640-500=140cc.$
But as mass of flask is $390g$, so density of material of flask
$\rho =\frac{m}{V}=\frac{390}{140}=2.8g/cc$