Answer: g/2.
- A g/2
- B g/4
- C 2g
- D g
Correct answer: A. g/2
Explanation: g' = g(1 − d/R) = g(1 − 1/2) = g/2.
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.