Question

if a planet exists whose mass and radius is half of that of earth then the acceleration due to gravity at the surface would be?

Answer 1

For earth, g = GM/R^2

For the other planet,

m = M/2

r = R/2

g' = GM/r^2 = G(M/2)/(R/2)^2

g' = 2 GM/R^2

g' = 2g

Thus the acceleration due to gravity on that planet will be twice of earth; that means 19.6 m/s^2