Question

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

• A. zero
• B. $15c{m}^3$
• C. $5c{m}^3$
• D. $20c{m}^3$

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 = $\frac{40}{8}=5c{m}^3$
Volume of cavity = (20 - 5)=. 15 cm${}^3$