Answer: -GM/r.
- A GMm/r
- B -GM/r
- C GM/r<sup>2</sup>
- D -GMm/r<sup>2</sup>
Correct answer: B. -GM/r
Explanation: Gravitational potential V = -GM/r (energy per unit mass). It is always negative.
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.