A planet is growing by accretion of material from the solar nebula. Suppose that as it grows, its density remains constant. Does the force of gravity at its surface increase, decrease, or stay the same? Why?

Question

Also, What would happen to the surface gravity as the radius of the planet doubled? Why?

Answer 1

The mass M is then proportional to the volume, so it is proportional to the third power of the radius. The force of gravity F at the surface is inversely proportional to the square of the radius and proportional to the mass:

F = proportional to M/R^2 = R

Answer 2

cannot understand your point

Answer 3

Are you saying that as the radius of the planet doubled the surface gravity would double too and it is because of the answer you gave before

Answer 4

The static value of gravity on, or above the surface of a spherical body is directly proportional to the mass of the body and inversely proportional to the square of the distance from the center of the body and is defined by the expression g = GM/r^2 = µ/r^2 where GM = µ = the gravitational constant of the body (G = the Universal Gravitational Constant and M = the mass of the body) and r = the distance from the center of the body to the point in question.

This should enable you to reach the conclusions you seek.