Question

An astronomical object has its mass 4 times the mass of earth and radius half of the radius of earth. If acceleration due to gravity at earth is g, find its value at the surface of the astronomical object.

Answer 1

g=GM/r²

m=4M..
r' = r/2...

so g' =Gm/r'²
. =G(4M) / (0.5r)²
. g'=16GM/r²
. g'=16g