Question

In air, a metallic sphere with an internal cavity weighs $40\,g$ and in water it weighs $20\,g$. The volume of cavity If the density of material with cavity be $8g/cm^3$ is

• A. zero
• B. $15\,cm^3$
• C. $5\,cm^3$
• D. $20\,cm^3$

Answer 1

Answer: (B)

Weight of sphere in air = 40 g
Weight of sphere in water = 20 g
Loss in weight = (40 - 20)g = 20 g
Weight of water displaced=loss in weight=20 g
Mass of water displaced = 20 cm
Actual volume of sphere = volume of water displaced = 20 cm$^3$
Volume of material in sphere = $\frac{40}{8} = 5 \, cm^3$
Volume of cavity = (20 - 5)=. 15 cm$^3$