Question

If mass of a planet is $10$% less than that of the Earth and radius $20$% greater than that of the Earth, then the acceleration due to gravity on the planet will be:

Answer 1

$g=\frac{GM}{R^2}$

Let $M\prime =M-\frac{M}{10}=\frac{9M}{10}$

$R\prime =R+\frac{R}{5}=\frac{6R}{5}$

$\therefore g\prime =\frac{G\times 9M\times 5}{10\times 6R\times 6R}=\frac{GM}{8R^2}=\frac{g}{8}$