Question

A particle of mass $10g$ is kept on the surface of a uniform sphere of mass $100kg$ and radius $10cm$. Find the work to be done against the gravitational force between them to take the particle far away from the sphere
(you may take $G=6.67\times {10}^{-11}{Nm}^2/{kg}^2$)

• A. $13.34\times {10}^{-10}J$
• B. $3.33\times {10}^{-10}J$
• C. $6.67\times {10}^{-9}J$
• D. $6.67\times {10}^{-10}J$

Answer 1

The correct option is D $6.67\times {10}^{-10}J$

Force between two masses are

$F=\frac{G{m}_1{m}_2}{r^2}=\frac{6.67\times {10}^{-11}\times 100\times 10\times {10}^{-3}}{(10\times {10}^{-2}{)}^2}=\frac{6.67\times {10}^{-11}}{{10}^{-2}}=6.67\times {10}^{-9}$