Question

A hypothetical planet has a radius 2.1 times that of Earth, but has the same mass. What is the acceleration due to gravity near its surface?

What equation should i use?

Answer 1

well, Force is proprotional to mass, which is the same, and inversly proportional to radius squared. That means the graviational field vector (g) is 9.8/2.1^2 N/kg or as you probably know it, 9.8/2.1^2 m/s^2, the acceleration do to gravity at the surface.