A hollow hemisphere has a mass of 8kg and radius of 10cm. Gravitational force on a mass of 8kg at the center of hemisphere is (approx.)

 $Gravitational field intensity at the centre of hollow hemisphere is ,E=\frac{GM}{2R^2}$

$$\begin{gathered} E=\frac{G\times 8}{2{\left(10\times {10}^{-2}\right)}^2} \\ E=\frac{6.67\times {10}^{-11}\times 8}{2\times {10}^{-2}}=26.68\times {10}^{-9} \\ E=2.7\times {10}^{-8}N/kg \\ \begin{array}{l}\therefore Gravitationalforceis\\ F=m\times E=8\times 2.7\times {10}^{-8}=21.6\times {10}^{-8}N\end{array} \end{gathered}$$