Question

The mass of Planet X is one-tenth that of the Earth, and its diameter is one-half that of the Earth. The acceleration due to gravity at the surface of Planet X is most nearly 

(A) 2m/s² 

 (B) 4m/s² 

 (C) 5 m/s² 

(D) 7 m/s² 

 (E) 10 m/s²

Answer 1

Correct option (B) 4 m/s²

g = GM/r² so the acceleration due to gravity (and the weight of an object) is proportional to the mass of the planet and inversely proportional to the distance from the center of the planet squared. M ÷ 10 = g ÷ 10 and r ÷ 2 = g × 4, so the net effect is g × 4/10.