To solve the problem we will apply the concept given by Newton for the definition of the gravity of a planet, for which he defines that this is proportional to the product of the mass of the planet by the universal gravitational constant, and inversely proportional to the square of the radius of the planet. Mathematically this can be described as
[tex]g = \frac{GM}{R^2}[/tex]
Here,
G = Gravitational Universal Constant
M = Mass of the planet, at this case Neptune
R = Radius of the planet, at this case Neptune
Replacing we have that
[tex]g = \frac{(6*10^{-11})(1.03*10^{26})}{2.21*10^7}[/tex]
[tex]g = 14.1m/s^2[/tex]
Therefore the acceleration due to gravity on Neptune is [tex]g = 14.1m/s^2[/tex]
