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A hemispherical depression is cut out from one face of a cubical wooden block such that the diameter $l$ of the hemisphere is equal to the edge of the cube. Determine the surface area of the remaining solid.
Given:
A hemispherical depression is cut out from one face of a cubical wooden block such that the diameter $l$ of the hemisphere is equal to the edge of the cube.
To do:
We have to find the surface area of the remaining solid.
Solution:
Edge of the cubical wooden block $a= l$
This implies,
Diameter of the hemisphere curved out of the cube $=l$
Radius of the hemisphere $r=\frac{l}{2}$
Therefore,
Volume of the cube $=a^{3}$
$=(l)^{3}$
$=l^3$ cubic units
Volume of the hemisphere $=\frac{2}{3} \pi r^{3}$
$=\frac{2}{3} \times \pi \times (\frac{l}{2})^3$
$=\frac{1}{12} \pi l^3$ cubic units
Total surface area of the remaining block $=6 a^{2}+2 \pi r^{2}-\pi r^{2}$
$=6 a^{2}+\pi r^{2}$
$=6 \times (l)^2+\pi \times (\frac{l}{2})^2$
$=l^2(6+\frac{\pi}{4})$
$=l^2(\frac{\pi+24}{4})$ square units
The total surface area of the remaining block is $l^2(\frac{\pi+24}{4})$ square units.