Question

A steel block having an internal cavity weighs $234g$ in air and $197g$ in water. If the density of steel is $7.8gc{m}^{-3}$, then the volume of the cavity is

• A. $5c{m}^3$
• B. $7c{m}^3$
• C. $9c{m}^3$
• D. $11c{m}^3$

Answer 1

The correct option is B $7c{m}^3$

Neglecting upward thrust for air,
Actual mass block$=234g$
Volume of steel in the block$=\frac{234}{7.8}c{m}^3=30c{m}^3$............1
Loss of weight when the block is immersed in water $=37gms$
So,
volume of water displaced $=37c{m}^3$..........2
From 1 and 2,
the volume of the cavity $=7c{m}^3$