A spherical metallic shell with 6 cm external radius weight 6688 g. What is the thickness of the shell if the density of metal is 10.5 g per cm3?

Answer: Option D

Solution

Answer: Option D

Solution:

$$\begin{array}{rl}& \text{Volume of Metallic shell}\\ & =V=\frac{4}{3}\pi \left(R^3-r^3\right)\\ & \text{Total weight of Metallic shell}\\ & \Rightarrow 10.5\times V=6688\\ & \Rightarrow 10.5\times \frac{4}{3}\times \frac{22}{7}\left(6^3-r^3\right)=6688\\ & \Rightarrow r=4\\ & \text{Thickness}=6-4=2\end{array}$$