Answer: g/4.
- A g/2
- B g/4
- C g/9
- D g
Correct answer: B. g/4
Explanation: g' = g R²/(R + h)² = g R²/(2R)² = g/4.
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.