Answer: GM/R2.
- A G/R2
- B GM/R2
- C GMm/R2
- D 2GM/R2
Correct answer: B. GM/R2
Explanation: Gravitational field intensity (force per unit mass) = GM/R2 = g (acceleration due to gravity at surface).
g is maximum at Earth's surface; going up, it falls off as 1/r² (inverse-square); going down, it falls off linearly with depth (since only the mass enclosed within radius r contributes), reaching zero at the centre.
Concept context
Universal gravitation, orbital mechanics, gravitational potential, and escape velocity.