A body weighs 63 N on the surface of the earth. How much will it weighs at a height equal to half the radius of the earth

Weight of a body on the surface of the earth$=63\text{N}$ 

The weight of a body is given by:
$\mathrm{w} = \mathrm{mg}$

where g is given by:
$\mathrm{g}=\frac{\mathrm{GM}}{{\mathrm{R}}^2}$

Let $g_h$ be acceleration due to gravity at a certain height h.

${\text{g}}_{\text{h}}=\frac{\text{GM}}{{\left(\text{R}+\text{h}\right)}^2}$

$\text{here h}=\frac{\text{R}}{\text{2}}$

$=\frac{\text{GM}}{{\left(\text{R}+\frac{\text{R}}{\text{2}}\right)}^2}\Rightarrow \frac{\text{GM}}{{\left(\frac{\text{2R+R}}{2}\right)}^2}\Rightarrow \frac{\text{4GM}}{9{\text{R}}^2}=\frac{4}{9}\text{g}$

${\text{g}}_{\text{h}}=\frac{4}{9}\text{g}$

Weight of a body at a height $\frac{\text{R}}{\text{2}}$  from the surface of the earth

${\text{mg}}_{\text{h}}=\frac{4}{9}\text{mg}$

${\text{mg}}_{\text{h}}=\frac{4}{9}\times 63\text{N}$  $\Rightarrow 28\text{N}$