Question

A spherical planet far out in space has a mass M and diameter D. A particle of mass m falling freely near the surface of this planet will experience an acceleration due to gravity which is equal to..?

Answer 1

as we know g = GM/R²
R= D/2 
so,
g = GM/ (D/2)²
 = 4GM/ D²

so as the mass of the planet = M
diameter = D
than g = 4GM/ D²

Answer 2

As the mass of planet= M

Diameter =D

So we have,g= GM/R^2

And radius is the half of diameter,

R= D/2

g= GM/(D/2)^2

=4GM/D^2