Question

The diameters of the internal and external surfaces of a hollow spherical shell are $6cm$ and $10cm$ respectively. If it is melted and recast into a solid cylinder of diameter $14cm$, find the height of the cylinder.

Answer 1

Volume of sphere = $V_s=\frac{4}{3}\pi (R_e^3-R_i^3)$

$V_s=\pi \times 7^2\times h$

$\Rightarrow h=\frac{4(5^3-3^3)}{3\times 7^2}=\frac{8}{3}cm$