MvCalc49

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Let the center of the sphere be at the origin and let the axis of the hole be along the z-axis. The volume V of the sphere is \frac{4}{3}\pi a^3\, and that of the circular hole is obtained as follows.

Volume of the upper half of the hole=\iint_R f(x,y)dx dy=\iint_R zdx dy\, where z is obtained from the equation x^2+y^2+z^2=a^2\, and R is the circle in the XY-plane,that is x^2+y^2=b^2\,.Hence,the volume V1 of the circular hole is

V_1=2\iint_R \sqrt{a^2-x^2-y^2}dx dy\, where R is given by x^2+y^2=b^2\,. Changing into polar coordinates,we obtain,

v_1=2\int_{0}^{2\pi}\int_0^b \sqrt{a^2-r^2} r dr d\theta=\frac{4\pi}{3}[a^3-(a^2-b^2)^{\frac{3}{2}}]\,

Hence the remaining portion =V-V_1=\frac{4\pi}{3}a^3-\frac{4\pi}{3}[a^3-(a^2-b^2)^{\frac{3}{2}}]=\frac{4\pi}{3}(a^2-b^2)^{\frac{3}{2}}\,

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