Question

If a person weighs $750N$ on earth, how much would be his weight on the moon given that moon's mass is $\frac{1}{81}$ of that of the earth and its radius is $\frac{1}{3.7}$ of that of the earth?

Answer 1

Weight on earth $=mg=750$
$m=\frac{750}{g}$
$g=\left(\frac{GM}{r^2}\right)$ on earth
Mass of moon, $M_m=\frac{m}{81}$
Radius of moon, $r_m=\frac{r}{3.7}$
$g_m=\frac{G{M}_m}{r_m^2}=0.169\left(\frac{GM}{r^2}\right)$
$g_m=0.169$
So, weight on moon $=m{g}_m$
$=\frac{250}{g}\times 0.169g$
$=126.759N$