The free-fall acceleration at the surface of planet 1 is 18 m/s^2. The radius and the mass of planet 2 are twice those of planet 1. What is the free-fall acceleration on planet 2?

Answer 1

g= GM/R^2
For Planet 1, Let it be g1=GM1/R1^2
And for planet 2, g2=GM2/R2^2[M2=2M1 and R2= 2 R1]
So g2=GM1/2R1^2
g2=g1/2=9m/s^2.
Hope this helped!!!