8.16 Assuming the earth to be a sphere of uniform mass density, how much would a body weigh half way down to the centre of the earth if it weighed 250 N on the surface?

Given,
Weight of a body of mass m at the Earth's Surface, W = mg = 250 N
Body of mass m is located at depth, d =12Re
Acceleration due to gravity at depth g (d) is given by the relation:
g=1-dReg

=1-Re2×Reg
=12g
Weight of the body at depth d,
W' = mg
=m×12g=12mg=12W
=12×250=125N